Add apply to project feature for worktree sessions

[built-by-as]

Summary

• Adds "Apply to project" option in the three-dot menu for worktree sessions
• Creates a confirmation modal showing branch details before applying changes
• Generates patch files that capture all commits and unstaged changes from the worktree branch
• Applies the patch to the original project directory
• Automatically cleans up temporary patch files after success or failure

Changes

UI Updates (renderer.ts, index.html)

• Added "Apply to project" menu item (only visible for worktree sessions)
• Created confirmation modal with branch name and parent branch display
• Shows warning that commits and unstaged changes will be included
• Handles button state (disabled/loading) during operation

Backend (main.ts)

• Added apply-session-to-project IPC handler
• Uses git diff <parent-branch> to capture all changes since branch diverged
• Writes patch to /tmp/fleetcode-patch-<timestamp>.patch
• Applies patch using git apply
• Deletes patch file on success or error
• Returns detailed error messages if patch fails to apply

Additional Improvements

• Shows last directory name in parentheses before full path in project directory input

Test plan

• Build completes successfully
• Create a worktree session
• Make some changes (commits + unstaged files)
• Click "Apply to project" from the three-dot menu
• Verify confirmation dialog shows correct branch info
• Confirm and verify changes are applied to original project directory
• Verify patch file is cleaned up from /tmp