feat(queue): durable local close queue with rate-limit retry (RUSH-2308)

[muqsitnawaz]

Linear close operations now survive rate limits and transient API failures via a durable local queue.

What changed

• linear update <id> --done --proof ... persists a close intent to ~/.linear-cli/queue/ before calling Linear. On a 429/transient error the intent is retained and retried later instead of being dropped.
• Added linear queue and linear queue drain (--dry-run) to inspect and apply queued closes.
• gql now surfaces HTTP status codes in GraphQL error extensions so callers can detect 429 vs permanent failures.
• Exponential bounded backoff (2s base, 5m cap) and bounded queue growth (1000 intents, 10 attempts) prevent unbounded retries.
• Idempotent: duplicate intents collapse to the latest proof/comment; already-closed issues are skipped.

Links

• Closes RUSH-2308 (implementation in linear-cli; consumer wiring remains in agents-cli per ticket scope)

Verification

• Unit tests: python3 -m unittest -v → 95 tests pass (full output)
• Local simulated rate-limit demo (full output):

=== 1. Simulated rate limit on linear update --done ===
STDOUT:
RUSH-DEMO -> queued for retry (rate limited / transient)

=== 2. Show queue ===
STDOUT:
1 close intent(s) queued:
  RUSH-DEMO -> Done (attempts=0)
Run `linear queue drain` to apply them.

=== 3. Drain queue (now succeeds) ===
STDOUT:
Applied RUSH-DEMO -> Done
Drained 1 intent(s). Queue empty.

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[muqsitnawaz]

Non-author review (recorded as comment — formal approve blocked since the codex agent opened this under my GH identity, but I did NOT author the code). VERDICT: PASS. Independently validated: ran 95 tests OK incl. durable-queue coverage; HTTP-status transient detection (429/502/503/504); idempotent backoff drain; bounded per-issue queue; API key never persisted. Merged on green.