[feature] RC: publish plan stages and tool completion from the host loop #301

Gap

In the #229 live journey the phone showed No plan reported yet for every run, and Tool activity only ever received tool_activity {status: started} — never a completion/failure — so the viewer filed started under history as a success. The host loop's stages (recon → parse → brainstorm → write-plans → execute → self-review → reveal) are never projected as plan events.

Acceptance

• Each host stage transition emits a bounded plan event (title + status).
• Each tool call emits a terminal tool_activity (completed/failed) after started.
• Tests through the real coding seam for local and hosted brains.

Refs #229 (evidence: Windows session events seq 7/11 only started).