Summary

Enhances the project file explorer sidebar with right-click actions and tab opening.

Note: this PR is stacked on #39808 (project file explorer sidebar). Once that merges, this diff will shrink to only the changes below.

Changes

• Right-click context menu on files/directories in the explorer: Rename and Delete. Uses a controlled \MenuV2\ dropdown positioned at the cursor (fixes the prior always-open menu bug).
• Rename dialog (\DialogV2\ + \TextInputV2, pre-filled name, Enter to confirm) and Delete confirmation dialog (danger button). \F2\ opens the rename dialog directly.
• Real filesystem operations via new desktop IPC channels
  ename-path\ and
  emove-path\ (node \s.rename\ / \s.rm), exposed through preload and the \Platform\ interface.
• Open file as tab: clicking a file in the explorer opens it as a tab in the existing session side panel (\layout.tabs(sessionKey).open) when a session is active; otherwise it navigates to the project session as before.
• New i18n keys for rename/delete across all locales.

Testing

• \�un typecheck\ in \packages/app\ and \packages/desktop\ (only pre-existing \custom-elements.d.ts\ error).
• File tree unit tests passing.
• Tested interactively in the desktop app.