fix: improve cross-platform compatibility for macOS and Linux

[mitre88]

Summary

Improves cross-platform robustness for macOS and Linux, addressing the "Windows-only testing" known limitation noted in the README.

Changes

1. Graceful fs.watch error handling (fileWatcher.ts)

• Added error event handler on the fs.watch watcher to prevent unhandled errors from crashing the extension
• On Linux, fs.watch can fail with ENOSPC when the system runs out of inotify watchers — the error message now includes a hint to increase fs.inotify.max_user_watches
• The existing triple-redundancy (fs.watch + fs.watchFile + polling) already provides excellent macOS support; this change ensures errors are handled cleanly rather than potentially propagating

2. Cross-platform asset path normalization (assetLoader.ts)

• The furniture catalog JSON stores file paths with POSIX separators (/). The path comparison (startsWith("assets/")) worked correctly, but the resolved path could theoretically mix separators on Windows
• Now normalizes catalog paths using path.posix/path.win32 and splits on / when joining, ensuring consistent behavior across all platforms

3. Platform logging on startup (PixelAgentsViewProvider.ts)

• Logs process.platform and process.arch at startup for easier debugging of platform-specific issues

4. Layout watcher error logging (layoutPersistence.ts)

• The fs.watch error handler for the layout file watcher previously swallowed errors silently — now logs them for debugging

Testing

• ✅ Full build (npm run build) passes on macOS (arm64, Darwin)
• ✅ TypeScript type-checking passes
• ✅ ESLint passes (via lint-staged)
• ✅ All changes are backwards-compatible — no behavioral changes on Windows

Notes

After reviewing the codebase thoroughly, the extension is already well-architected for cross-platform use:

• All file paths use path.join() consistently
• File watching already uses triple redundancy (fs.watch + fs.watchFile + manual polling)
• The project directory naming (getProjectDirPath) matches Claude Code's own convention across platforms

These changes are defensive improvements that handle edge cases (fs.watch errors, path normalization) and improve debuggability on non-Windows platforms.