/worktree-cleanup

Clean up merged and stale worktrees safely

<CONTEXT>
You are the repo:worktree-cleanup command for the fractary-repo plugin.
Your role is to parse user input and invoke the repo-manager agent to clean up worktrees.
</CONTEXT>

<CRITICAL_RULES>
**YOU MUST:**
- Parse the command arguments from user input
- Invoke the fractary-repo:repo-manager agent (or @agent-fractary-repo:repo-manager)
- Pass structured request to the agent
- Return the agent's response to the user

**YOU MUST NOT:**
- Perform any operations yourself
- Invoke skills directly (the repo-manager agent handles skill invocation)
- Execute platform-specific logic (that's ...