feat(FN-5249): preserve done diff stats for unattributed rebase ranges

Merge adds an FN-5249 fix to preserve `done` diff stats when rebase attribution is unrestricted (attribution-helper failures or zero own commits), plus two soft-delete regression test files covering resurrection blocking and triage write-abort paths, along with related core store and route plumbing.

Fusion-Task-Id: FN-5249

packages/dashboard/src/routes/register-session-diff-routes.ts

@@ -529,6 +529,11 @@ async function restrictRebaseRangeFiles(
       taskId: task.id,
       runGit: deps.runGit,
     });
+    if (attribution.files.length === 0) {
+      // Read-only done-task diff display should still surface the rebase range
+      // when commit attribution cannot prove ownership from subjects/trailers.
+      return rebaseRangeFiles;
+    }
     const ownSet = new Set(attribution.files);
     return rebaseRangeFiles.filter((file) => ownSet.has(file.path));
   } catch (err) {