fix(council-v2): serialize topicTicker to prevent fire-and-forget concurrency

executorLoop fire-and-forgets each effect execution. Multiple concurrent
execute() calls each invoke topicTicker(), causing concurrent tick() calls
that bypass Moore diff (both read same prevSnapshotJson before either updates).

Fix: chain tick() calls via promise serialization. Critical section
(read → diff → update baseline) is now guaranteed sequential.

packages/pulse/src/topics/index.ts

@@ -22,9 +22,17 @@ import type { TopicRule } from './topic-rule-adapter.js';
  * suitable for calling at the end of a runPulse tick cycle.
  */
 export function createTopicTicker(rules: TopicRule[]): () => Promise<void> {
-  return async () => {
-    for (const rule of rules) {
-      await rule.tick();
-    }
+  let pending: Promise<void> | null = null;
+  return () => {
+    // Serialize tick calls: if a tick is in progress, chain after it.
+    // This ensures the Moore machine's critical section (read → diff → update baseline)
+    // is never concurrent, even when called from fire-and-forget executors.
+    const run = async () => {
+      for (const rule of rules) {
+        await rule.tick();
+      }
+    };
+    pending = (pending ?? Promise.resolve()).then(run, run);
+    return pending;
   };
 }