test(voice): cover tts fallback

docs/plans/state.json

@@ -6737,10 +6737,24 @@
         "docs/plans/state.json"
       ],
       "test_status": "pnpm test:run src/gateway/canvas-store.test.ts src/gateway/ui/pages/chat.test.ts passing"
+    },
+    "deeper-surfaces-phase3-voice-continuity": {
+      "status": "completed",
+      "date": "2026-02-25",
+      "updated": "2026-02-25",
+      "summary": "Verified voice continuity by adding explicit test coverage for TTS synthesis failure fallbacks and documenting the text-only degradation behavior in protocol/architecture notes.",
+      "files_modified": [
+        "src/daemon/routing.test.ts",
+        "docs/api/PROTOCOL.md",
+        "docs/architecture/AGENT_DIAGRAM.md",
+        "docs/architecture/GATEWAY_SESSIONS_AND_QUEUE.md",
+        "docs/plans/state.json"
+      ],
+      "test_status": "pnpm test:run src/daemon/routing.test.ts passing"
     }
   },
   "overall_progress": {
-    "total_test_count": 2021,
+    "total_test_count": 2022,
     "all_tests_passing": true,
     "p0_completion": "3/3 (100%)",
     "p1_completion": "4/4 (100%)",