[Feature Request] Add CLI command for programmatic session renaming

Feature Request

Add a CLI command to rename sessions without entering interactive mode.

Use Case

I want to integrate Claude Code session management with WezTerm (or other terminal multiplexers) to rename sessions
from outside the Claude CLI.

Proposed API

claude session rename <old-name-or-id> <new-name>
# or
claude --rename-session <name> --session-id <id>

Current Workaround

Must use /rename interactively or press R in the session picker — no way to script this.

Additional Context

Exposing session metadata as JSON or providing a claude session subcommand group would enable better tooling
integration.

**Environment Info**
- Platform: darwin
- Terminal: WezTerm
- Version: 2.1.14
- Feedback ID: a0354294-670f-4f68-aaed-21ba8f6c06be