test: assert the interval pause, and document accessor non-reactivity

Splitting the interval spies from the rAF ones left both unasserted, so
deleting pauseChangeDetection() from destroy() went unnoticed here. The
cleanup case now asserts one spy per loop.

Also carries the plain-number caveat onto the interface, which is the
surface a new consumer reads before the implementation.

Author: benjcooley

src/renderer/core/layout/types.ts

@@ -271,7 +271,12 @@ export interface LayoutChange {
 export interface LayoutStore {
   /** Node count, without materialising layouts as `getAllNodes()` does. */
   readonly nodeCount: number
-  /** Cache key for derived structures; see the implementation for its scope. */
+  /**
+   * Cache key for derived structures; see the implementation for its scope.
+   *
+   * Plain numbers on a non-reactive class instance: reading either inside a
+   * `computed` or `watch` tracks nothing and never re-evaluates. Poll them.
+   */
   readonly layoutVersion: number
   /** Cache key for geometry-derived state; moves only when nodes move. */
   readonly nodeGeometryVersion: number

src/renderer/extensions/minimap/composables/useMinimap.test.ts

@@ -427,7 +427,10 @@ describe('useMinimap', () => {
       await minimap.init()
       minimap.destroy()
 
+      // Both loops: rAF drives viewport sync, the interval drives change
+      // detection. One spy each, or deleting either pause here goes unnoticed.
       expect(mockPause).toHaveBeenCalled()
+      expect(mockIntervalPause).toHaveBeenCalled()
       expect(api.removeEventListener).toHaveBeenCalledWith(
         'graphChanged',
         expect.any(Function)