Auto-generate meaningful session names from conversation context

Feature Request

When using claude --resume, sessions are identified by opaque IDs which makes it difficult to find the right session to resume. Users must manually /rename every session to make them identifiable.

Proposal

Auto-generate a short descriptive session name based on the first user prompt or conversation topic. For example:

• bugfix-kafka-lifecycle
• forge-yaml-dedup
• investigate-dd-tags

This would make the resume picker significantly more usable without requiring manual /rename each session.

Current behavior

Sessions show as IDs in the --resume picker, making it hard to distinguish between them.

Desired behavior

• Automatically generate a 2-4 word descriptive name from the initial prompt or early conversation context
• Fall back to the current ID system if auto-naming fails
• Still allow /rename to override the auto-generated name

This is a small quality-of-life improvement that would reduce friction for power users who frequently resume sessions.