fix(desktop): track isDisabled flips in the adapter no-op notify gate

Review follow-up: __internal_setAdapter assigned this.isDisabled before
the fast path but never fed it into the new 'changed' flag, so an
isDisabled-only flip on an otherwise-identical adapter swap would have
been silently swallowed. Seed 'changed' with the isDisabled comparison
and add a guard test (mutation-checked: reverting the seed fails it).

apps/desktop/src/lib/incremental-external-store-runtime.ts

@@ -146,7 +146,9 @@ class IncrementalExternalStoreThreadRuntimeCore extends ExternalStoreThreadRunti
     }
 
     const isRunning = store.isRunning ?? false
-    this.isDisabled = store.isDisabled ?? false
+    const newDisabled = store.isDisabled ?? false
+    const disabledChanged = this.isDisabled !== newDisabled
+    this.isDisabled = newDisabled
 
     const oldStore = self._store
     self._store = store
@@ -158,7 +160,7 @@ class IncrementalExternalStoreThreadRuntimeCore extends ExternalStoreThreadRunti
     // (render -> new literal -> setAdapter -> notify -> render), which React
     // kills with "Maximum update depth exceeded" and takes the session tile
     // down with its error boundary.
-    let changed = false
+    let changed = disabledChanged
 
     if (this.extras !== store.extras) {
       this.extras = store.extras

apps/desktop/src/lib/incremental-runtime-adapter-notify.test.ts

@@ -115,6 +115,29 @@ describe('IncrementalExternalStoreThreadRuntimeCore adapter swap notifications',
     expect(notifications).toBeGreaterThan(0)
   })
 
+  it('still notifies on an isDisabled flip even when transcript and run state are unchanged', () => {
+    const repo = repositoryOf([message('a', 'one')])
+    const core = new IncrementalExternalStoreRuntimeCore(adapterWith(repo))
+    const thread = core.threads.getMainThreadRuntimeCore()
+
+    let notifications = 0
+    thread.subscribe(() => {
+      notifications += 1
+    })
+
+    core.setAdapter(adapterWith(repo, { isDisabled: true }))
+
+    expect(notifications).toBeGreaterThan(0)
+
+    // And flipping back also notifies — but an unchanged repeat stays silent.
+    core.setAdapter(adapterWith(repo, { isDisabled: false }))
+    const afterFlipBack = notifications
+
+    core.setAdapter(adapterWith(repo, { isDisabled: false }))
+
+    expect(notifications).toBe(afterFlipBack)
+  })
+
   it('a subscriber that swaps a fresh-but-identical adapter on every notify must not recurse unboundedly', () => {
     // Direct simulation of the feedback loop: the subscriber plays the role of
     // React re-rendering ChatRuntimeBoundary (new literal -> setAdapter). With