feat: rebuild reactivity state from store after replay

Add `rebuildReactivityFromStore` to synchronize local reactivity
state with the hydrated variable store. This ensures tag activations
are correctly tracked following a reducer replay.

Also remove the unused `invalidateCompletions` function.

src/components/journal/completions.ts

@@ -209,12 +209,6 @@ export function ensureCompletions(): Promise<void> {
   return _initPromise;
 }
 
-/** Force a re-fetch on the next page load. For runtime, call before invalidate triggers. */
-let _invalidated = false;
-export function invalidateCompletions(): void {
-  _invalidated = true;
-}
-
 /**
  * Reactive hooks for the journal input.
  * Returns the current completions state + a convenience `data` extractor.

src/components/journal/index.ts

@@ -48,7 +48,7 @@ export { StreamMessageCard } from "./StreamMessage";
 export { ComposePanel } from "./ComposePanel";
 export { JournalInput } from "./JournalInput";
 export { DynamicForm } from "./DynamicForm";
-export { useJournalCompletions, invalidateCompletions } from "./completions";
+export { useJournalCompletions } from "./completions";
 export { dispatchCommand } from "./command-dispatcher";
 export type { DispatchContext, DispatchResult } from "./command-dispatcher";
 export { parseInput } from "./command-parser";

src/components/journal/var-reactivity.ts

@@ -167,6 +167,27 @@ export function setBase(key: string, value: string): void {
   baseValues.set(key, value);
 }
 
+/**
+ * Rebuild local reactivity state (baseValues, activeMods, sourceActivations)
+ * from the hydrated stream variable store. Must be called after replayReducers
+ * so that tag activations are correctly tracked for subsequent cascade
+ * computations.
+ */
+export function rebuildReactivityFromStore(variables: VariableStore): void {
+  if (!tagModMap) return;
+
+  for (const [key, value] of Object.entries(variables)) {
+    if (!baseValues.has(key)) {
+      baseValues.set(key, value);
+    }
+
+    const tag = isTagValue(value);
+    if (tag && !sourceActivations.has(key)) {
+      activateTagFromSource(key, tag, variables);
+    }
+  }
+}
+
 /**
  * Compute cascade effects after a variable change.
  *

src/components/stores/journalStream.ts

@@ -14,6 +14,7 @@ import { createSignal } from "solid-js";
 import * as Comlink from "comlink";
 import type { StreamMessage } from "../journal/registry";
 import { getMessageType, validatePayload } from "../journal/registry";
+import { rebuildReactivityFromStore } from "../journal/var-reactivity";
 import type { WorkerState, WorkerPatch, SessionManifest } from "../../workers/journal.worker";
 import type { JournalWorkerAPI } from "../../workers/journal.worker";
 import {
@@ -162,6 +163,9 @@ function handlePatch(patch: WorkerPatch): void {
       saveRole(patch.state.myRole);
       // Rebuild derived state (revealedPaths, variables) by replaying reducers
       replayReducers();
+      // Rebuild local reactivity engine state so tag activations from
+      // hydrated variables are tracked for subsequent cascade computations.
+      rebuildReactivityFromStore(state.variables);
       break;
     }