Add ForwardSlashPath branded type and forward-slash path utilities

[Copilot]

Summary

Centralizes all replaceAll("\\", "/") path normalization behind a suite of utility functions that return a branded ForwardSlashPath type, enabling static enforcement that backslash-to-forward-slash conversion has occurred before a path is used in contexts that require it (chokidar watchers, ES module specifiers, URL routing).

// Before — scattered inline normalization
this.basePath = basePath.replaceAll("\\", "/");
const fullPath = nodePath.join(destination, path).replaceAll("\\", "/");

// After — centralized, typed, enforced
this.basePath = toForwardSlashPath(basePath);
const fullPath = pathJoin(destination, path); // returns ForwardSlashPath

New utility (src/util/forward-slash-path.ts):

• ForwardSlashPath — branded type (string & { readonly [__forwardSlashPath]: never }) using a unique symbol to prevent accidental assignment of un-normalized strings
• toForwardSlashPath(path: string): ForwardSlashPath — the core normalization function
• pathJoin(...paths: string[]): ForwardSlashPath — wraps nodePath.join, returning a forward-slash path
• pathRelative(from: string, to: string): ForwardSlashPath — wraps nodePath.relative, returning a forward-slash path
• pathDirname(path: string): ForwardSlashPath — wraps nodePath.dirname, returning a forward-slash path
• pathResolve(...paths: string[]): ForwardSlashPath — wraps nodePath.resolve, returning a forward-slash path

Updated call sites — 13 files replaced inline .replaceAll("\\", "/") and toForwardSlashPath(nodePath.xxx(...)) patterns with the new utilities:

• src/server/ — file-discovery.ts, module-loader.ts, transpiler.ts
• src/typescript-generator/ — repository.ts, script.ts, generate.ts, operation-coder.ts, operation-type-coder.ts, parameters-type-coder.ts, prune.ts
• src/migrate/update-route-types.ts, src/app.ts, bin/counterfact.js

Several files (transpiler.ts, script.ts, operation-coder.ts, operation-type-coder.ts, parameters-type-coder.ts, file-discovery.ts, app.ts) no longer import nodePath at all.

Test updates:

• test/server/transpiler.test.ts — removed local forwardSlash helper; now imports toForwardSlashPath
• test/util/forward-slash-path.test.ts — 14 unit tests covering all exported functions

Original Prompt

Create a utility function to replace replaceAll("\", "/") throughout the code.

Return a branded string and use that branded string wherever a path without backslashes is needed.

Manual acceptance tests

• toForwardSlashPath("C:\\Users\\foo\\bar") returns "C:/Users/foo/bar" with no backslashes remaining
• pathJoin("routes", "pets.ts") returns "routes/pets.ts" (forward slashes, cross-platform)
• pathRelative("/a/b", "/a/b/c") returns "c" (forward slashes, cross-platform)
• Server starts and handles requests normally — no regression in path-based routing
• TypeScript compiler rejects assigning a plain string to a ForwardSlashPath-typed variable without going through one of the utility functions

Tasks

• Created src/util/forward-slash-path.ts with ForwardSlashPath branded type, toForwardSlashPath, and four nodePath-wrapping helpers (pathJoin, pathRelative, pathDirname, pathResolve)
• Replaced all inline .replaceAll("\\", "/") occurrences across 13 source files with toForwardSlashPath or the appropriate wrapper
• Replaced all toForwardSlashPath(nodePath.xxx(...)) call-site patterns with the corresponding wrapper function
• Updated test/server/transpiler.test.ts to import toForwardSlashPath instead of using a local helper
• Added test/util/forward-slash-path.test.ts with 14 unit tests covering all exported functions
• Added changeset (patch bump)

[pmcelhaney]

The new function is mostly used to fix the output of nodePath.join() or nodePath.relative()

Create two new utility functions that wrap the nodePath functions so we can eliminate duplication.

[Copilot]

The new function is mostly used to fix the output of nodePath.join() or nodePath.relative()

Create two new utility functions that wrap the nodePath functions so we can eliminate duplication.

Done in commit 9faad6a. Added four wrapper functions to src/util/forward-slash-path.ts:

• pathJoin(...paths) — wraps nodePath.join
• pathRelative(from, to) — wraps nodePath.relative
• pathDirname(path) — wraps nodePath.dirname
• pathResolve(...paths) — wraps nodePath.resolve

All call sites updated; several files no longer import nodePath at all.