Auto-name sessions based on first message

Feature Request

Sessions are currently saved with UUIDs (e.g., 83a7286b-4714-4b4e-bd1e-300b199b59f6) and require manual /rename to give them meaningful names. This makes --resume hard to use since you're guessing which session was which.

Proposal

Auto-generate a short descriptive session name based on the overall content/theme of the session (not just the first message). Since session memory already writes continuous summaries in the background, this summary could be used to derive a meaningful name.

For example:

• Session about setting up dark mode → setup-dark-mode
• Session debugging auth token refresh → debug-auth-token-refresh
• Session doing a usage audit across chat history → claude-usage-audit

Current Workaround

Manually running /rename <name> after starting each session. Easy to forget, and most sessions end up unnamed.

Why This Matters

• claude --resume shows a list of sessions — unnamed UUIDs are useless for picking the right one
• Power users with 100+ sessions can't find anything without names
• Session memory already captures the context needed to generate a good name

Suggested Behavior

• Auto-name after enough context exists (e.g., after session memory writes its first summary)
• Update the name if the session topic shifts significantly
• Keep /rename for manual overrides
• Name format: lowercase-kebab-case, max ~50 chars, derived from session summary