Tier GitHub PR lookup polling to prevent quota exhaustion (#12013)

* Tier GitHub PR lookup polling to prevent quota exhaustion

The selected worktree (O(1)) checks per-minute; card list (O(N)) per-15-minutes.
Introduce process-wide cache to collapse concurrent polling and gate lookups on
available rate-limit budget with exponential backoff on failure.

- Preserve last-known review during backoff
- Invalidate cache when Orca opens a PR
- Stop coordinator from double-charging

* Tier GitHub PR lookup polling to prevent quota exhaustion

- Return the latest reset time when both GitHub API buckets are rate-limited, preventing premature retries against still-blocked buckets.
- Serve the last known review on transient lookup failures, preventing reviews from blinking out on temporary errors.
- Discard in-flight lookups that predate an invalidation so stale answers cannot overwrite newly opened reviews.

* fix: give rate-limit reset tests unique titles

oxlint vitest/no-identical-title was failing static analysis because two
cases shared the same describe title.

src/main/github/pr-refresh-coordinator.test.ts

@@ -649,18 +649,9 @@ describe('pr-refresh-coordinator', () => {
       'graphql',
       executionOptions
     )
-    expect(noteRepositoryRateLimitSpendMock).toHaveBeenCalledWith(
-      testCase.repository,
-      'core',
-      1,
-      executionOptions
-    )
-    expect(noteRepositoryRateLimitSpendMock).toHaveBeenCalledWith(
-      testCase.repository,
-      'graphql',
-      1,
-      executionOptions
-    )
+    // Why (#11532): the lookup itself debits the snapshot now, so every caller
+    // is accounted for; the coordinator must not double-charge on top.
+    expect(noteRepositoryRateLimitSpendMock).not.toHaveBeenCalled()
     expect(getPRForBranchOutcomeMock).toHaveBeenCalledTimes(1)
   })