docs(state): sync state.json after phase 19.4 planning

.planning/state.json

@@ -173,11 +173,6 @@
       "name": "Chat satellites",
       "status": "complete"
     },
-    {
-      "number": "19.2",
-      "name": "Chat polish against WavePath clients",
-      "status": "pending"
-    },
     {
       "number": "19.3",
       "name": "Framework transport and infrastructure for WavePath",
@@ -205,14 +200,24 @@
     },
     {
       "number": "20",
+      "name": "Demo instance with every shared plugin",
+      "status": "pending"
+    },
+    {
+      "number": "30",
       "name": "Płytarium cutover",
       "status": "pending"
+    },
+    {
+      "number": "31",
+      "name": "Chat polish against WavePath clients",
+      "status": "pending"
     }
   ],
   "next": {
     "command": "/msd:progress --next",
-    "label": "Advance to the next step (plan phase 19.2)",
-    "reason": "Phase 19.2 of 41 — needs a plan"
+    "label": "Advance to the next step",
+    "reason": "Phase 19.4 of 42 · executing"
   },
-  "updated_at": "2026-10-18T17:25:43.481Z"
+  "updated_at": "2026-10-19T15:59:56.706Z"
 }