Move the #971 tests into the director suite and add the changelog fragment

The standalone director971.test.mjs rebuilt the browser, storage and viewer
doubles that director.test.mjs already provides. Its cases now live in the
director suite on makeDirector/installSceneRuntime, which gains optional
seeded storage entries and a quota-full switch; existing tests are unchanged.
The checkpoint and failed-save-status cases are split so each fails on its own.

changelog.d/1135-director-save-status-run-results.md

@@ -0,0 +1,5 @@
+- Scenes keep the "Scene not saved" status when a capture, update, append or
+  import cannot be saved, and an unreadable saved project no longer overwrites
+  the recovery checkpoint. `startScene()` resolves to its documented result,
+  `afterShotId` works without an explicit scene, and `scenesRun` counts the
+  distinct scenes queued (djabhi31, #1135).