Add shutdown outcome telemetry to LLM queue worker - #2746

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Fresh-context review record (coordinator, 2026-09-06; read-only Opus 5 reviewer over the diff against the merge base; route: the standing D-12 rule for Codex-session PRs — review, fix MEDIUM+ in-PR, merge, disposition comment).

VERDICT: FIX-FIRST (round 1) → fixed (round 2, coordinator commit 2f6531cea; LlmQueueToProposalWorkerTests plus WorkerResilienceTests 67/67 locally). HIGH-1 — the test helper listened to the process-global WorkerItemsProcessed counter, filtered only on the outcome tag, appended to an unsynchronised List<string> and asserted exact single-element sequences, while TranscriptTriageWorkerTests, the webhook worker tests and both WorkerResilienceTests classes drive the same counter in parallel collections: intermittent reds on unrelated PRs and a data race. The test class now sits in a DisableParallelization collection, the listener filters on worker.name and locks the list. MEDIUM-2 — abandoned_shutdown was emitted exactly when the row was successfully released (nothing abandoned) and nothing at all when the release write failed; the outcomes are now released_on_shutdown and shutdown_release_failed, the latter recorded only from the release write's catch (a row that had already moved on emits nothing, which the retry-backoff cancellation test pins). Recorded, not fixed (LOW): RecordWorkerOutcome sits inside the requeue try, so a throwing meter listener after a committed requeue logs the opposite of the persisted state; CompleteRetryTransitionOnShutdownAsync returns true on a no-op transition, so cancelled_requeued can count a requeue that did not occur; the second negative control asserts NotContain where BeEmpty would be the real control. Confirmed clean: the #2620 cooperative-stop contract, tag cardinality, no ids or content in tags, layer purity.