fix(security): active guard enforcement, CEO A2A target check, notification expiry (#595)

* fix(security): guard goes active; CEO A2A respects no-comms roles; ack notifications expire

ROBOCO_GUARD_PASSIVE_MODE defaults to false in both compose files — the
deferred post-calibration flip; fail_secure stays off and the env override
remains the rollback. can_a2a_direct no longer short-circuits the CEO past
the no-comms set (auditor/pr_reviewer/prompter/secretary), now canonical
in foundation.policy.communications.NO_COMMS_ROLES and shared with the
content-actions gate; the A2A service refuses at conversation creation
instead of silently suppressing the wake. Ack-required notifications get
expires_at stamped from ROBOCO_NOTIFICATION_ACK_TTL_HOURS (default 48,
0 disables), so the re-escalation sweeper's expires_at query matches rows
for the first time.

* refactor(notification): extract _ack_and_expiry — xenon rank back under B

The expires_at stamping pushed _create_notification_with_session to
rank C; the requires_ack + expiry derivation moves into a helper with
the same semantics and comments.

* test(conftest): dispose the global DB engine after every test

Production code reaching get_db_context()/get_engine() lazily creates the
process-global engine bound to the current event loop; with per-test
function-scoped loops, any later test touching the global path inherits a
dead-loop engine and dies with 'Future attached to a different loop' —
the order-dependent class that has been wandering the suite (cloud_auth
login, metrics, tasks-routes, full-lifecycle) whenever collection order
shifts. An autouse fixture now close_db()s after every test, keeping the
global path loop-local; no-op when untouched.

---------

Co-authored-by: Renn F <rennf93@users.noreply.github.com>

docker-compose.registry.yml

@@ -35,9 +35,11 @@
 #     stays conservative; the build compose arms most of them ON for the
 #     personal NAS deploy. ROBOCO_ROUTING_STRICT and the fastapi-guard trio
 #     (ROBOCO_GUARD_ENABLED/_PASSIVE_MODE/_FAIL_SECURE) are the exception:
-#     both are still mid-calibration on the personal deploy, so they're
-#     omitted entirely here rather than carried — their config defaults
-#     (graceful-degrade routing, guard off) are already the safe posture.
+#     ROUTING_STRICT is still mid-calibration, and guard is now ACTIVE
+#     enforcement on the personal deploy (passive calibration reviewed clean).
+#     Both stay omitted here rather than carried — a third-party deployer
+#     hasn't run that calibration against their own traffic, so their config
+#     defaults (graceful-degrade routing, guard off) are the safer posture.
 #   - Host path defaults differ (/opt/roboco vs /volume1/roboco, ${HOME}
 #     instead of a hardcoded /home/renzof) — registry targets a generic host.
 #   - MinIO (object storage for rendered videos) is intentionally omitted —