Add 'Open in Explorer' / 'Open folder in Explorer' to file-tree and sidebar

[leo-3889]

Summary

Adds a right-click "open in the OS file manager" affordance in two places, so you can jump from the UI straight into Explorer / Finder / xdg-open for a project or a specific folder.

• Sidebar Files button — right-click shows a single "Open in Explorer" (Finder / File Manager, per-OS) item that opens the project's directory.
• File-tree context menus —
  • right-click a folder → "Open in Explorer" opens that folder;
  • right-click a file → "Open folder in Explorer" opens its parent directory.

Labels are i18n'd (en + zh-CN) and chosen per OS so they read naturally.

How it works

• New app:openInFileManager IPC (main ipc-handlers.ts) → shell.openPath(dir), exposed through preload as window.vibeyard.app.openInFileManager.
• Shared per-OS label helper in src/renderer/file-manager-label.ts, reused by both the sidebar and the file tree.
• File-tree menus reuse the existing showContextMenu + deleteMenuOption machinery; no new DOM/CSS.

Testing

• npm run build — all three targets compile.
• npm test — 1868 pass. The one failure is a pre-existing, environment-specific Windows locale issue in big-initial-context.test.ts (expects 50,000, gets 50.000); unrelated to these changes and present on upstream main too.

No main/preload behavior changes beyond the new IPC handler.

[elirantutia]

Thanks for this — sorry for the timing: this landed on main in a7684ab before I got to the PR. That version adds path validation, lstat so symlinks aren't followed, macOS package handling, and reveal-with-selection for files.

Closing as superseded. Appreciate the contribution.

[leo-3889]

No worries, as long as we have the feature coming that's great !