Auto-name sessions based on conversation context

Feature Request

Problem: Sessions start unnamed, requiring manual /rename to give them a useful label. This adds friction, especially when managing many sessions via /resume.

Proposed behavior:
After the first user message (or first few exchanges), automatically generate a short, descriptive session name based on the conversation context, similar to how ChatGPT auto-titles conversations.

Bonus: Allow assigning a random color or tag to sessions for visual differentiation in the /resume picker.

Current workarounds:

• claude --name "name" at startup (requires knowing the topic in advance)
• /rename mid-session (manual, easy to forget)
• Shell alias with random string (not descriptive)

None of these provide the ideal UX of a context-aware auto-generated name.

Suggested implementation:

• After the first assistant response, derive a 2-4 word summary and set it as the session name
• Allow the user to override with /rename at any time
• Optional: make auto-naming configurable (on/off) in settings