fix: old folder persists in sidebar after drag-and-drop move

[chirag-bruno]

Summary

• Broadcast unlinkDir event after directory move so the old folder is removed from the sidebar

Problem

When dragging a folder into another folder, the folder appeared in the new location but the old folder remained visible in the sidebar. The move couldn't be "reverted" because the stale folder entry persisted.

Root Cause

VS Code's createFileSystemWatcher only watches file patterns (**/*.bru / **/*.yml), not directory deletions. When removePath deletes a folder during a move, the watcher fires unlink events for the .bru files inside but not for the directory itself. The Redux store never received an unlinkDir event, so the empty folder node stayed in the collection tree.

Solution

After removePath completes in the renderer:move-item handler, check if the source was a directory and broadcast an unlinkDir event to all webviews. The existing collectionUnlinkDirectoryEvent reducer handles the removal from the Redux store.

Test plan

• Drag a folder into another folder → verify old folder disappears from sidebar
• Drag the folder back out → verify it moves correctly and old location is cleaned up
• Drag a request file (not folder) → verify normal move still works
• TypeScript typecheck passes

JIRA: https://usebruno.atlassian.net/browse/VSCODE-46