review: fix 26 findings from a 4-agent audit

CORRECTNESS
- lost-lease race: complete()/fail() did not check ownership, so a worker whose
  lease expired could mark a task done while another worker was running it, or
  requeue a task someone else owned. Reproduced, fixed with a CAS on
  (state, locked_by), pinned by two regression tests.
- worker died on report failure: _run_one's docstring claimed no exception
  escapes the TaskGroup; fail()/complete() were outside the guarded block, so a
  DB blip cancelled every sibling provision on the pod.
- claim query used an INNER join, which could strand a just-claimed task and
  report 'queue empty'. LEFT join.
- InstanceRepo.set_error bypassed the state machine and had no callers. Deleted.
- handle_deprovision ignored its CAS result, so a wrong-state instance kept a
  dangling endpoint and got re-provisioned by the drift check 60s later.
- handle_verify re-notified on every retry: five pages for one halt.

DEPLOY-BREAKING
- the migration Job could never succeed: no Dockerfile copied migrations/, and
  migrate.py resolved the path relative to the source tree, which only works for
  an editable install. Added COPY + SVCFORGE_MIGRATIONS_DIR.
- ServiceMonitor selector did not match the Service: API metrics never scraped.
- SvcforgeReconcilerStale fired permanently from every pod, because the gauge is
  module-level and every service exports it as 0. Scoped to the reconciler job.
- SvcforgeTaskFailed latched forever on a monotonic counter. Now increase()[15m].
- the digest guard accepted the all-zeros placeholder.
- worker terminationGracePeriodSeconds was 60s against a 600s helm timeout.

DEAD CODE THAT SHOULD NOT HAVE BEEN
- adapters/k8s.py was never called, so tenant namespaces were never created and
  the first provision for a new team would fail. Wired into handle_provision.
- adapters/redis.py was never imported by any service. Rate limiting is now wired
  into the API, failing open.
- Settings.check_production() had no callers. Given an explicit environment and
  called from every entrypoint.

OBSERVABILITY
- the API never called obs.setup(): no JSON logs, no trace correlation, log_json
  silently inert.
- LogNotifier's structured fields were discarded by the stdlib->structlog bridge.
- bind_task_context cleared the 'service' binding for the life of every task.
- split tasks_failed into task_attempts_failed and tasks_dead_lettered.

SECURITY
- trivy correctly blocked the worker/reconciler images: helm 3.16.2 and kubectl
  1.31.2 carry CRITICAL Go stdlib CVEs. Bumped to helm 3.21.3 and kubectl 1.35.3,
  which also closes a four-minor skew against the v1.35.3 cluster.

TESTS THAT COULD NOT FAIL
- the concurrency cap test passed on a fully serial worker.
- the alert/metric cross-check asserted a hardcoded list instead of reading the
  chart, so it could not catch a rename on the chart side.
- fixed OTel tracer-provider pollution between test files.

DOCS
- ARCHITECTURE.md: mermaid diagrams, user stories, and the helm-vs-ArgoCD
  guarantee (verified with --dry-run=server).
- AGENTS.md + CLAUDE.md.
- prose sweep for back-and-forth phrasing across 19 files.

deploy/chart/templates/worker-deployment.yaml

@@ -25,9 +25,19 @@ spec:
         {{- toYaml . | nindent 8 }}
       {{- end }}
       # The load-bearing one. On SIGTERM the loop stops claiming and finishes the task in
-      # hand; 60s is the budget for that. Chaos experiment 2 asserts the pod exits 0 inside
-      # it. Lower this and a rolling deploy starts orphaning tasks to lease expiry.
-      terminationGracePeriodSeconds: 60
+      # hand. Chaos experiment 2 asserts the pod exits 0 inside it. Lower this and a
+      # rolling deploy starts orphaning tasks to lease expiry.
+      #
+      # 660s, and the number is derived, not chosen. The task being drained is a
+      # `helm upgrade --install`, and this MUST exceed the longest that call can run before
+      # it returns:
+      #   - settings.py           helm_timeout_s  = 300  (default)
+      #   - HelmProvisioner       timeout_s       = 600  (default, the ceiling)
+      # 600s is the value to beat; 660 leaves a 60s margin for the pool to close and the
+      # process to exit cleanly. At the old 60s the kubelet SIGKILLed the worker mid-helm —
+      # precisely the orphaning this setting exists to prevent. If either timeout above is
+      # raised, raise this past it first.
+      terminationGracePeriodSeconds: 660
       securityContext:
         {{- include "svcforge.podSecurityContext" . | nindent 8 }}
       containers: