Hook event for recap text

Feature request

It would be useful to have a hook event that fires when a recap is generated, with the recap text available to the hook (e.g. via stdin JSON like PreToolUse/PostToolUse).

Use case

We use hooks to bridge Claude Code activity to a chat system (Rains federation via River MCP). Currently we post progress updates manually via MCP tool calls, but a PostRecap or OnRecap hook would let us automatically forward the harness-generated summary to external systems without relying on the LLM to remember to do it.

The recap text is already a good concise summary of what happened — being able to pipe it somewhere automatically would be valuable.

Suggested behavior

• New hook event (e.g. PostRecap or OnRecap)
• Fires after the recap is generated
• stdin JSON includes at minimum: recap_text, session_id, transcript_path
• Hook stdout could optionally replace/modify the displayed recap (similar to how PreToolUse can block)