feat: workspaces, agentic action tools, local Whisper STT, vec recall

- Projects/workspaces: documents grouped into projects; chat RAG scopes to the
  active project. Switcher in the Documents page.
- Agentic action tools: web_search, fetch_url, and remember (first write tool),
  allowlist-gated per playbook.
- Local Whisper STT (faster-whisper, no torch): on-device dictation replacing
  the browser Web Speech API. POST /stt + GET /stt/status; browser fallback.
- Vector index extended to conversation recall (message_vectors), with the
  brute-force cosine scan kept as the fallback.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

tests/test_smoke.py

@@ -43,6 +43,13 @@ def test_keep_alive_pins_the_model():
     assert "keep_alive" not in mgr._apply_keep_alive({"model": "x"})
 
 
+def test_stt_status_endpoint():
+    # Reports whether local Whisper is installed; wiring must respond either way.
+    resp = TestClient(app).get("/stt/status")
+    assert resp.status_code == 200
+    assert isinstance(resp.json()["available"], bool)
+
+
 def test_num_ctx_option_only_when_positive():
     # 0 / None -> omit num_ctx so Ollama uses the model default; positive -> set it.
     from synapse.ollama_manager import _chat_options