fix(FR-2157): prevent double rebuild on config.toml change

[nowgnuesLee]

Resolves #5621 (FR-2157)

Summary

When config.toml is modified during development, the browser was reloading twice instead of once. This was caused by two independent mechanisms both triggering reloads:

1. webpack context dependency: When webpack resolves aliases outside react/ (e.g. backend.ai-client-esm → ../dist/lib/...), enhanced-resolve walks up the directory tree and adds the project root as a context dependency. This causes webpack to detect config.toml changes → recompile → HMR finds no module updates → falls back to full page reload.

2. fs.watch dying on atomic save: IDEs like VS Code use atomic save (write temp → rename), which replaces the file's inode. fs.watch watches the old inode and stops detecting changes, leaving only the webpack-triggered reload (which itself fires twice due to temp file + rename events).

Changes

• watchOptions.ignored: string array → RegExp — Ignore all files directly in the project root ([^/]+$ pattern) to catch both config files AND editor temp files. dist/ and packages/ subdirectories remain watched for HMR.
• fs.watch → fs.watchFile for individual files — Polling-based watching (500ms interval) survives file replacements from atomic save. Directories (resources/i18n) still use fs.watch.
• Shared debounce timer (300ms) — All watchers share a single timer to coalesce rapid events into one reload signal.

Verification

scripts/verify.sh: ALL PASS (Relay, Lint, Format, TypeScript)

Tested with Chrome DevTools monitoring:

• Server sends exactly 1 static-changed WebSocket message per config.toml edit
• webpack does NOT recompile (no "Compiling..." in terminal)
• Browser reloads exactly once

Test plan

• Run dev server and modify config.toml from IDE — verify only ONE reload occurs
• Verify HMR still works for React source changes
• Verify dist/lib/backend.ai-client-esm.js changes still trigger HMR
• Verify index.html changes still trigger a page reload
• Verify i18n translation file changes still trigger a page reload
• Verify resources/theme.json changes still trigger a page reload
• Production build (pnpm run build) completes successfully

🤖 Generated with Claude Code

[nowgnuesLee]

• fix(FR-2157): prevent double rebuild on config.toml change #5749 👈 (View in Graphite)
• main

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[Copilot]

Pull request overview

Adjusts the React dev-server / webpack watcher configuration to stop config.toml edits from triggering redundant rebuild + reload cycles during development, especially with editors that use atomic-save semantics.

Changes:

• Consolidates dev-server reload signaling behind a shared debounce to coalesce rapid watcher events.
• Switches per-file watching from fs.watch to fs.watchFile (polling) to survive atomic-save inode replacement.
• Replaces watchOptions.ignored string-array configuration with a single RegExp intended to ignore project-root files (and temp files) to prevent webpack rebuilds.

[yomybaby]

LGTM

[graphite-app]

Merge activity

• Mar 10, 5:37 AM UTC: yomybaby added this pull request to the Graphite merge queue.
• Mar 10, 5:39 AM UTC: Merged by the Graphite merge queue.