Allow programmatic /rename from within a session

Use case

I run a multi-agent system where each session has a structured ID (e.g., S062-shared-repo). At clockin, the agent knows the session ID and slug. I'd like the conversation to be automatically named so I can find it later via /resume.

Currently /rename is user-only — the AI can't invoke it, and there's no tool/hook/API to rename programmatically.

Proposed solution

Any of these would work:

1. Allow the AI to call /rename as a built-in command (like it can use other tools)
2. Add a conversation.rename hook event so a shell script can rename after clockin
3. Expose a --rename flag on the CLI that can be called from within a running session

Why it matters

Without programmatic rename, every session shows up as an auto-generated or unnamed entry in /resume. For users with structured session workflows, this makes /resume nearly useless — you can't tell sessions apart. A single rename call at session start would make the full conversation history navigable.

Current workaround

The greeting includes a suggested /rename S062-slug for the user to paste manually. Works but adds friction to every session.