fix: address second review — agent path, display name, signal subtype

- plugin.json: use ./agents/workshop-ta.md path format (matches all other plugins)
- workshop-ta front matter: name 'Workshop TA' preserves acronym (was 'workshop-ta')
- signal-write: add subtype field (hands-up/blocked/done/checkpoint/partnership)
  so dashboard consumers can distinguish specific signal states
- npm run build: regenerated docs/README.agents.md

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Copilot-Session: 26faf13e-639c-4a21-ac05-c0dc2bff7c62

agents/workshop-ta.agent.md

@@ -1,5 +1,5 @@
 ---
-name: workshop-ta
+name: Workshop TA
 description: 'Room coordinator for a multi-agent workshop. Sees all desks, routes work, tracks state, manages journals, and emits coordination signals. Not a desk — the person who sees the whole room.'
 ---