feat: add WebUI Press content mode

DESIGN.md

@@ -4945,8 +4945,43 @@ The adapter handles all outputs in one `onEnd` pass.
 
 ### webui-press integration
 
+`DocsConfig.show` is a typed `ShowMode` (`all` or `content`), defaulting to
+`all`. Both native `build` and `serve` accept `--show`; an explicit CLI value
+overrides configuration on the initial build and every serve config reload.
+Page and 404 build errors retain the core error's complete source chain,
+including parser diagnostic codes, locations, snippets, and help when present.
+
+Content mode selects the bundled content document before region expansion,
+component/script reachability, compilation, and SSR. It retains document
+metadata, base URL, configured head tags, themes, authored page modules, state,
+and semantic `main`/`article` wrappers. Markdown (including home Markdown),
+custom-page HTML, examples, and API panels are content, regardless of their
+element names. No template regions, navigation, sidebar/TOC, mobile context,
+previous/next links, hero/features, footer, or shell scripts are generated.
+Configured regions remain validated against the selected full template, but
+their state and scripts are inactive. This also applies to the 404 document.
+
+The bundled `docs.css` contains shared tokens and content typography;
+`shell.css` contains full-site layout constraints. All mode concatenates both
+into one served stylesheet, preserving the existing layout without an extra
+request. Content mode uses only the bundled content styles, normal document
+scrolling, and no shell width/height constraints. A custom full template and
+its styles/entry script do not replace the content-mode scaffold; configured
+head tags, CSS/theme, components, and custom pages continue to apply.
+
+Full-site manual light/dark selection overrides the OS preference for both
+native theme tokens and `color-scheme`. Manual overrides are inactive under
+forced colors so site-authored forced-colors token rules retain precedence.
+Content mode has no shell theme control, does not read or snapshot a persisted
+theme into `data-theme`, and uses only the light default and system dark media
+query. It follows live OS preference changes without JavaScript and leaves the
+stored full-site preference untouched.
+
 `webui-press` invokes esbuild's JavaScript API once through
 `@microsoft/webui/projection.js`, then validates the generated manifest once.
+Filesystem alias targets are resolved against an absolute config directory
+before passing them to esbuild. Relative and absolute CLI config paths retain
+the same config-relative alias semantics, independent of the invocation cwd.
 The resulting `PreparedProjectionManifests` is reused by every page and the 404
 build; page builds never re-open or re-hash bundle files. The prepared handle
 is an `Arc`-backed immutable snapshot containing both component surfaces and

crates/webui-press/Cargo.toml

@@ -50,3 +50,6 @@ microsoft-webui-dev-server = { path = "../webui-dev-server", version = "0.0.28"
 actix-web = { workspace = true }
 tokio = { workspace = true }
 include_dir = { workspace = true }
+
+[dev-dependencies]
+tempfile = { workspace = true }

crates/webui-press/README.md

@@ -125,13 +125,40 @@ Every `.md` file under `contentDir` becomes a page automatically. The sidebar/na
 
 ```
 webui-press build [OPTIONS]
+webui-press serve [OPTIONS]
 
 Options:
   -c, --config <PATH>      Path to config.json [default: .webui-press/config.json]
   -t, --template <PATH>    Override the bundled template directory
+      --show <MODE>        all or content [default: config show, otherwise all]
   -h, --help               Print help
 ```
 
+Use `webui-press build --show=content` or `webui-press serve --show=content`
+for a shell-free gallery or documentation view. Omit the flag for the complete
+site, or set `"show": "content"` in config to make content mode the default.
+An explicit flag overrides config, including after live config reloads.
+
+Content mode keeps a complete HTML document, metadata/base URL, themes, SSR,
+hydration, Markdown, examples, API panels, custom-page content, and page scripts.
+It omits Press template regions, hero/features, header/navigation,
+sidebars/TOC, mobile navigation, previous/next links, and footer before
+compilation. Authored header/side-pane examples are not filtered. Home Markdown
+is rendered in this mode; doc, page, full, custom, and 404 pages all use normal
+document scrolling without reserved shell columns or viewport-fill behavior.
+
+Content mode uses the bundled `main`/`article` scaffold even with `--template`.
+Its colors follow the OS preference, including live changes, without reading
+or changing the full site's saved theme selection. Full mode retains its
+persisted theme control; manual light/dark selection applies to native theme
+tokens and browser controls even when the OS preference differs. Forced-colors
+styles retain precedence over manual theme overrides.
+
+The full template's regions are still validated but are inactive, as are its
+CSS and entry script. Configure `head`, `css`, `theme`, `components`, and page
+scripts for assets that should apply in both modes. In the bundled full template,
+shared `docs.css` and layout-only `shell.css` are combined into one output file.
+
 The build pipeline:
 
 ```

crates/webui-press/src/build.rs

@@ -28,7 +28,7 @@ use crate::error::{Error, Result};
 use crate::markdown::Highlighter;
 use crate::regions::RegionSet;
 use crate::state::{load_render_states, merge_page_state};
-use crate::types::{BuildStats, DocsConfig, PageDescriptor};
+use crate::types::{BuildStats, DocsConfig, PageDescriptor, ShowMode};
 
 webui_handler::define_string_response_writer!(StringWriter, buf);
 
@@ -41,6 +41,27 @@ fn region_layout(page: &PageDescriptor) -> &str {
     }
 }
 
+fn template_css(template_dir: &Path, show: ShowMode) -> Result<String> {
+    if show == ShowMode::Content {
+        return Ok(include_str!("../template/docs.css").to_string());
+    }
+    let mut css = String::new();
+    for name in ["docs.css", "shell.css"] {
+        let path = template_dir.join(name);
+        match fs::read_to_string(&path) {
+            Ok(source) => css.push_str(&source),
+            Err(error) if error.kind() == std::io::ErrorKind::NotFound => {}
+            Err(error) => {
+                return Err(Error::Io(format!(
+                    "Cannot read {}: {error}",
+                    path.display()
+                )));
+            }
+        }
+    }
+    Ok(css)
+}
+
 /// Persistent state held by the dev server across rebuilds. The dev
 /// server always performs a full rebuild on every watcher tick — the
 /// previous incremental machinery proved too complex for the marginal
@@ -298,8 +319,8 @@ pub fn build_docs_with_cache(
     // the link tags change. We don't write the CSS files yet — that
     // happens after content processing succeeds, so a content failure
     // can't corrupt the previous valid output.
-    let base_css_src = template_dir.join("docs.css");
-    let has_base_css = base_css_src.exists();
+    let base_css = template_css(template_dir, config.show)?;
+    let has_base_css = !base_css.is_empty();
     let base_css_link = if has_base_css {
         format!("<link rel=\"stylesheet\" href=\"{base_path}docs.css\">")
     } else {
@@ -361,6 +382,17 @@ pub fn build_docs_with_cache(
     let template_html = fs::read_to_string(template_dir.join("index.html"))
         .map_err(|e| Error::Build(format!("Failed to read template: {e}")))?;
     let regions = RegionSet::load(&config.regions, config_dir, template_html)?;
+    // Validate configured region names even when the selected presentation
+    // makes every shell region inactive. Authored page content is never filtered.
+    let regions = if config.show == ShowMode::Content {
+        RegionSet::load(
+            &Default::default(),
+            config_dir,
+            include_str!("../template/content.html").to_string(),
+        )?
+    } else {
+        regions
+    };
     let component_script_index = discover_component_scripts(&component_sources)?;
 
     // Step 3: Wipe the previous output and recreate the site root.
@@ -379,8 +411,8 @@ pub fn build_docs_with_cache(
     // because we clean before processing — but that order means a
     // failure leaves no output at all, never half-output).
     if has_base_css {
-        fs::copy(&base_css_src, site_dir.join("docs.css"))
-            .map_err(|e| Error::Io(format!("Cannot copy docs.css: {e}")))?;
+        fs::write(site_dir.join("docs.css"), &base_css)
+            .map_err(|e| Error::Io(format!("Cannot write docs.css: {e}")))?;
     }
     if has_theme_css {
         fs::write(site_dir.join("theme.css"), &custom_css)
@@ -453,7 +485,7 @@ pub fn build_docs_with_cache(
     );
 
     let template_script_path = template_dir.join("index.ts");
-    let template_script = if template_script_path.exists() {
+    let template_script = if config.show == ShowMode::All && template_script_path.exists() {
         Some(
             template_script_path
                 .canonicalize()
@@ -663,7 +695,7 @@ pub fn build_docs_with_cache(
             projection_manifests: vec![projection_source.clone()],
             ..BuildOptions::default()
         })
-        .map_err(|e| Error::Build(format!("{}: {e}", page.path)))?;
+        .map_err(|e| Error::Build(format!("{}: {}", page.path, e.chain_message())))?;
         let preloads = generated_preloads.get().ok_or_else(|| {
             Error::Build("Generated preload metadata was not published".to_string())
         })?;
@@ -807,7 +839,7 @@ pub fn build_docs_with_cache(
         projection_manifests: vec![projection_source],
         ..BuildOptions::default()
     })
-    .map_err(|e| Error::Build(format!("404 build failed: {e}")))?;
+    .map_err(|e| Error::Build(format!("404 build failed: {}", e.chain_message())))?;
     let preloads = generated_preloads
         .get()
         .ok_or_else(|| Error::Build("Generated preload metadata was not published".to_string()))?;

crates/webui-press/src/bundler.rs

@@ -1202,7 +1202,8 @@ fn normalized_alias_target(config_dir: &Path, target: &str) -> String {
     target.replace('\\', "/")
 }
 
-fn build_aliases(opts: &BundleOptions<'_>) -> BTreeMap<String, String> {
+fn build_aliases(opts: &BundleOptions<'_>) -> Result<BTreeMap<String, String>> {
+    let config_dir = absolute_path(opts.config_dir)?;
     let mut aliases: BTreeMap<String, String> = BTreeMap::new();
     if let Some(node_modules) = opts.node_modules {
         if let Some(path) = default_framework_alias(node_modules) {
@@ -1212,11 +1213,11 @@ fn build_aliases(opts: &BundleOptions<'_>) -> BTreeMap<String, String> {
 
     if let Some(cfg) = opts.bundler_config {
         for (from, to) in &cfg.alias {
-            aliases.insert(from.clone(), normalized_alias_target(opts.config_dir, to));
+            aliases.insert(from.clone(), normalized_alias_target(&config_dir, to));
         }
     }
 
-    aliases
+    Ok(aliases)
 }
 
 #[cfg(test)]
@@ -1238,8 +1239,8 @@ fn esbuild_args(
     opts: &BundleOptions<'_>,
     entry_files: &[(String, PathBuf)],
     bundle_tmp: &Path,
-) -> Vec<String> {
-    let aliases = build_aliases(opts);
+) -> Result<Vec<String>> {
+    let aliases = build_aliases(opts)?;
     let target = opts
         .bundler_config
         .and_then(|cfg| cfg.target.as_deref())
@@ -1275,7 +1276,7 @@ fn esbuild_args(
     for (_, path) in entry_files {
         args.push(path_for_js(path));
     }
-    args
+    Ok(args)
 }
 
 fn esbuild_build_config(
@@ -1288,7 +1289,7 @@ fn esbuild_build_config(
     let working_dir = absolute_path(opts.config_dir)?;
     let site_dir = absolute_path(opts.site_dir)?;
     let manifest_path = absolute_path(manifest_path)?;
-    let aliases = build_aliases(opts);
+    let aliases = build_aliases(opts)?;
     let target = opts
         .bundler_config
         .and_then(|cfg| cfg.target.as_deref())
@@ -2051,7 +2052,7 @@ mod tests {
     }
 
     #[test]
-    fn esbuild_args_force_webui_decorator_semantics() {
+    fn esbuild_args_force_webui_decorator_semantics() -> TestResult {
         let site_dir = Path::new("/site");
         let config_dir = Path::new("/site/.webui-press");
         let opts = BundleOptions {
@@ -2065,13 +2066,14 @@ mod tests {
             config_dir,
             content_dir: Path::new("/site"),
         };
-        let args = esbuild_args(&opts, &[], Path::new("/tmp/webui-press-bundle"));
+        let args = esbuild_args(&opts, &[], Path::new("/tmp/webui-press-bundle"))?;
 
         assert!(args.contains(&format!("--tsconfig-raw={WEBUI_TSCONFIG_RAW}")));
+        Ok(())
     }
 
     #[test]
-    fn esbuild_args_folds_webui_dev_flag_for_production_only() {
+    fn esbuild_args_folds_webui_dev_flag_for_production_only() -> TestResult {
         fn opts<'a>(
             site_dir: &'a Path,
             config_dir: &'a Path,
@@ -2097,20 +2099,20 @@ mod tests {
 
         // Production build: the flag is folded to `false` so the framework's
         // dev-only diagnostics (and the module gating them) tree-shake out.
-        let prod = esbuild_args(&opts(site_dir, config_dir, false, None), &[], tmp);
+        let prod = esbuild_args(&opts(site_dir, config_dir, false, None), &[], tmp)?;
         assert!(prod.contains(&define));
 
         // Development build (`webui-press serve`): the flag is left undefined so
         // the `typeof` guard defaults it to on and diagnostics run.
-        let dev = esbuild_args(&opts(site_dir, config_dir, true, None), &[], tmp);
+        let dev = esbuild_args(&opts(site_dir, config_dir, true, None), &[], tmp)?;
         assert!(!dev.iter().any(|arg| arg.contains("__WEBUI_DEV__")));
 
         // A user-supplied define wins: esbuild honors the last `--define` for a
         // key, so our production default must be emitted before user defines.
         let mut cfg = BundlerConfig::default();
         cfg.define
             .insert("__WEBUI_DEV__".to_string(), "true".to_string());
-        let overridden = esbuild_args(&opts(site_dir, config_dir, false, Some(&cfg)), &[], tmp);
+        let overridden = esbuild_args(&opts(site_dir, config_dir, false, Some(&cfg)), &[], tmp)?;
         let ours = overridden.iter().position(|arg| arg == &define);
         let theirs = overridden
             .iter()
@@ -2121,6 +2123,7 @@ mod tests {
             ours < theirs,
             "framework default must precede the user override so esbuild's last-wins keeps the user's value",
         );
+        Ok(())
     }
 
     #[test]

crates/webui-press/src/content.rs

@@ -12,7 +12,7 @@ use serde_json::{Map, Value};
 use crate::error::{Error, Result};
 use crate::markdown::{render_markdown, Highlighter};
 use crate::state::{load_render_states, merge_page_state, LoadedStates};
-use crate::types::{DocsConfig, NavLink, PageDescriptor, SidebarItem, SidebarSection};
+use crate::types::{DocsConfig, NavLink, PageDescriptor, ShowMode, SidebarItem, SidebarSection};
 
 /// Normalize a config link (e.g. `/guide/intro/` or `/guide/intro`) to a
 /// canonical URL path that includes the site's `base_path` prefix and
@@ -518,7 +518,7 @@ pub(crate) fn process_content_with_states(
                         fm.layout.unwrap_or_else(|| "doc".to_string())
                     };
 
-                    if !is_home {
+                    if !is_home || config.show == ShowMode::Content {
                         // Canonical page URL: every page is written as
                         // `<dir>/index.html`, so it is served with a trailing
                         // slash. In-page anchors need this exact path so they