Expose session rename via MCP / SDK

Feature request

What: Add a rename_session tool to the ccd_session_mgmt MCP server, analogous to the existing list_sessions / archive_session tools.

Why: When Claude completes a well-defined task (e.g. a daily monitoring run), it knows a meaningful name for the session — but cannot apply it. The user has to rename manually via the UI. This is friction that could be eliminated if rename were exposed as a tool call.

Use case: A Claude Code agent runs a nightly production monitoring pipeline, scores results, creates an email draft, and at the end renames the session to "Daily Monitor — BF6 | 11.06.2026" — so the user's left panel stays organised without any manual steps.

Context: The current ccd_session_mgmt server exposes list_sessions, search_session_transcripts, send_message, and archive_session. Rename is the obvious missing primitive to complete session lifecycle management from within an agent.