Feature Request: CompanionMessage hook event

Problem

Buddy speech bubbles disappear after a few seconds with no way to capture them programmatically.
Users who want to log, forward, or re-use buddy messages currently have no hook to attach to.

This single gap blocks several use cases that already have open issues:

• #42186 — log buddy output to session JSONL
• #42767 — retrieve past buddy messages
• #42864 — configurable display duration
• #42865 — inject buddy message into Claude's conversation context

Proposed Hook

Add a CompanionMessage hook event that fires whenever the buddy emits a speech bubble.

Payload:

{
  "hook_event_name": "CompanionMessage",
  "companion_name": "Cobbler",
  "companion_species": "robot",
  "message": "Ah, user broke flow mid-tool. Found another one.",
  "session_id": "abc123"
}

Why a Hook (vs. built-in logging)

A hook lets users implement their own solution without Anthropic shipping N separate features:

• Log to file → solves #42186, #42767
• Send to Slack/Telegram → team visibility
• Append to session JSONL → works with existing tools like claude-history
• Inject into next prompt → solves #42865

One hook, five problems solved.

Related Issues

#42186 #42767 #42864 #42865 #41980