Feature request: Allow skills/hooks to set session title programmatically

Feature Request

Problem

When using skills (slash commands) to automate workflows — e.g., a /work skill that picks up the next sprint task — there's no way to update the session title to reflect what's being worked on. This makes it hard to identify sessions at a glance in the session picker.

Desired Behavior

A mechanism for skills or hooks to set the session title programmatically. For example:

• A SetSessionTitle tool available within skill execution
• A hook output field that allows setting the title (e.g., in PostToolUse or a new PostSkill hook)
• A CLI flag like claude session rename --id <id> --title "S1-07: Wave spawner"

Use Case

A /work skill that:

1. Finds the next undone sprint task (e.g., S1-07: Wave Spawner System)
2. Creates a branch and starts implementation
3. Sets the session title to something like S1-07: Wave Spawner System so the user can identify the session later

This is especially useful in multi-agent/multi-session workflows where many sessions are created and the auto-generated titles don't capture the task context.

Alternatives Considered

• Writing to a file-based state file — works for context recovery but doesn't help with session identification in the UI
• Status line updates — useful but separate from session naming