Wire up file actions in Associated Files dropdown

[IanMayo]

Summary

The Associated Files dropdown in the ActivityPanel shows context menu actions (Open, Open With, Reveal in Explorer, Delete) but these aren't functional yet.

Current State

• AssociatedFilesDropdown component renders the actions and calls onFileAction(file, action)
• LayersToolbar accepts onFileAction prop
• ActivityPanel does NOT pass onFileAction through to LayersToolbar
• No message handler in activityPanelView.ts

Implementation Needed

1. Add onFileAction prop to ActivityPanelProps in shared/components/src/ActivityPanel/types.ts
2. Pass callback to LayersToolbar in ActivityPanel.tsx
3. Add file:action message type to ActivityPanelMessage union
4. Handle message in activityPanelView.ts:
   • open: Open file in VS Code editor
   • openWith: Show "Open With..." picker
   • reveal: Reveal in file explorer (vscode.commands.executeCommand('revealFileInOS', uri))
   • delete: Delete file with confirmation

Note: In the apps/web-client version we should popup a dialog simulating the above actions, to show users what would happen.

Related

• Feature 048: Refactor VS Code map wrapper
• ActivityPanel component integration