chore(desktop): preserve appearance during CDP diagnostics

AGENTS.md

@@ -10,6 +10,12 @@
 - The script discovers the server with `opencode service status`, injects its private local credential from `opencode service get password`, and uses the `dev` TUI storage channel so tabs and other client-local state match the installed client.
 - Prefer `dev:live` over plain `bun run dev` for this workflow. An implicit managed-service connection may replace the live server when the worktree client version differs; explicit `--server` warns and continues without replacing it.
 
+## Live Desktop Diagnostics
+
+- When attaching Playwright to a running desktop app, use `chromium.connectOverCDP(endpoint, { noDefaults: true })`.
+- Without `noDefaults`, Playwright applies light-mode media emulation during attachment. An app following the system theme then flashes light until the connection closes. The option also preserves the existing focus and other media preferences.
+- Do not emulate a color scheme or reduced-motion preference on the user's live window unless explicitly requested; use an isolated test context for those scenarios.
+
 ## TUI Stories
 
 - When a user asks for a TUI story, add a fixture-driven story under `packages/tui/src/feature-plugins/system/storybook` and register it in `index.tsx`.

packages/app/e2e/performance/devex/desktop-startup.ts

@@ -239,7 +239,8 @@ function startDesktop(profile: Awaited<ReturnType<typeof createColdProfile>>) {
         }),
       ])
 
-      browser = await chromium.connectOverCDP(url, { timeout: 120_000 })
+      // Observe the native appearance and focus instead of applying Playwright's media defaults.
+      browser = await chromium.connectOverCDP(url, { timeout: 120_000, noDefaults: true })
       const context = browser.contexts()[0]
 
       if (!context) throw new Error("Electron did not expose a browser context")