Auto-name sessions from first user message

Feature Request

Claude.ai and ChatGPT both auto-generate a conversation title from the first user message. Claude Code (CLI) doesn't - sessions stay unnamed unless you manually /rename or pass --name at launch.

Current Workaround

Adding a rule in CLAUDE.md like:

At the start of every conversation, rename the session (/rename) to a short descriptive name based on the user's first message.

This is best-effort and gets missed. Hooks can't trigger /rename either, so there's no reliable automation path.

Proposed Behavior

After the first assistant response, auto-generate a short session name (2-4 words) from the user's first message. Same behavior as Claude.ai's auto-titling. The user can still override with /rename.

This would make /resume much more useful since sessions would have meaningful names by default instead of timestamps.