fix(github): harden terminal PR revalidation after critical review

Recompute focus/visibility staleness at event time, retry closed/merged
sidebar associations on the no-PR cadence, and assert refresh failures
preserve prior PR status.

Co-authored-by: Serhii Dziupin <makeittech@users.noreply.github.com>

packages/ui/src/stores/useGitHubPrStatusStore.ts

@@ -501,6 +501,8 @@ export const useGitHubPrStatusStore = create<GitHubPrStatusStore>()(
             if (!entry || entry.watchers <= 0) {
               return;
             }
+            // Bootstrap retries only help discovery before any PR is known. Once a
+            // terminal PR is cached, the discovery interval owns revalidation.
             if (entry.status?.pr) {
               return;
             }