fix: address CodeRabbit review findings

- Guard deactivate() against inactive tracker to prevent store() from
  freezing wrong viewport/output data into the old tracker
- Update docs: workflowService calls captureCanvasState indirectly via
  deactivate/prepareForSave, not directly
- Add deprecated checkState() to mock utility for extension compat
- Update deactivate test: inactive path is now a full no-op

docs/architecture/change-tracker.md

@@ -59,7 +59,7 @@ useWorkflowStore().activeWorkflow?.changeTracker?.captureCanvasState()
 
 ### Existing Manual Call Sites
 
-These locations already call `captureCanvasState()` explicitly:
+These locations call `captureCanvasState()` directly:
 
 - `WidgetSelectDropdown.vue` — After dropdown selection and file upload
 - `ColorPickerButton.vue` — After changing node colors
@@ -71,7 +71,9 @@ These locations already call `captureCanvasState()` explicitly:
 - `useSubgraphOperations.ts` — After subgraph enter/exit
 - `useCanvasRefresh.ts` — After canvas refresh
 - `useCoreCommands.ts` — After metadata/subgraph commands
-- `workflowService.ts` — After workflow service operations
+
+`workflowService.ts` calls `captureCanvasState()` indirectly via
+`deactivate()` and `prepareForSave()` (see Lifecycle Methods above).
 
 ## Lifecycle Methods
 

src/scripts/changeTracker.test.ts

@@ -223,14 +223,14 @@ describe('ChangeTracker', () => {
       expect(mockSubgraphNavigationStore.exportState).toHaveBeenCalled()
     })
 
-    it('still stores viewport when captureCanvasState is no-op (inactive)', () => {
+    it('is a full no-op when called on inactive tracker', () => {
       const tracker = createTracker()
       mockWorkflowStore.activeWorkflow = { changeTracker: {} }
 
       tracker.deactivate()
 
       expect(app.rootGraph.serialize).not.toHaveBeenCalled()
-      expect(mockNodeOutputStore.snapshotOutputs).toHaveBeenCalled()
+      expect(mockNodeOutputStore.snapshotOutputs).not.toHaveBeenCalled()
     })
   })
 

src/scripts/changeTracker.ts

@@ -97,10 +97,20 @@ export class ChangeTracker {
    * Called exactly once when switching away from this workflow.
    *
    * PRECONDITION: must be called while this workflow is still the active one
-   * (before the activeWorkflow pointer is moved). captureCanvasState() will
-   * no-op if called after the pointer has already moved.
+   * (before the activeWorkflow pointer is moved). If called after the pointer
+   * has already moved, this is a no-op to avoid freezing wrong viewport data.
    */
   deactivate() {
+    const isActive = useWorkflowStore().activeWorkflow?.changeTracker === this
+    if (!isActive) {
+      if (import.meta.env.DEV) {
+        logger.error(
+          'deactivate() called on inactive tracker for:',
+          this.workflow.path
+        )
+      }
+      return
+    }
     this.captureCanvasState()
     this.store()
   }

src/utils/__tests__/litegraphTestUtils.ts

@@ -257,6 +257,7 @@ export function createMockChangeTracker(
     redoQueue: [],
     changeCount: 0,
     captureCanvasState: vi.fn(),
+    checkState: vi.fn(),
     deactivate: vi.fn(),
     prepareForSave: vi.fn(),
     reset: vi.fn(),