[AZ-680] [AZ-681] operator_bridge command dispatch + safety lane

Add the operator-command dispatcher behind a typed CommandAck:
60 s per-command-id idempotency cache, surfaced-POI registry with
unknown_poi_id + expired gates, BIT-degraded ack severity check, and
SafetyOverride forwarding to mission_executor with structured audit
log (redacts signature + session_token).

Cross-layer wiring goes through three new traits in shared::contracts
(ScanCommandRouter, MissionSafetyRouter, BitReportSeverityLookup) so
operator_bridge stays free of direct scan_controller / mission_executor
imports. scan_controller::ScanControllerHandle implements the scan
router; a new mission_executor::SafetyDispatchHandle wraps the BIT
ack channel + battery monitor handle and implements the safety router;
BitControllerHandle gains a bounded (16-entry) report-severity cache
for the lookup trait.

scan_controller also picks up ConfirmPoi handling: PoiQueue::confirm
removes the entry and SubmitOutcome::Confirmed carries the typed
(target_mgrs, target_class) hint for AZ-684/AZ-686 downstream.

Tests: 9 new integration tests in operator_bridge/tests/dispatcher.rs
cover AZ-680 AC-1..AC-5 + AZ-681 AC-1..AC-4. scan_controller adds 2
ConfirmPoi tests. All modified-crate suites green; one pre-existing
mission_executor state-machine test flake (already documented in
_docs/_process_leftovers) updated to note ac1 also affected.

Co-authored-by: Cursor <cursoragent@cursor.com>

Cargo.lock

@@ -2244,6 +2244,7 @@ checksum = "9774ba4a74de5f7b1c1451ed6cd5285a32eddb5cccb8cc655a4e50009e06477f"
 name = "scan_controller"
 version = "0.1.0"
 dependencies = [
+ "async-trait",
  "chrono",
  "gimbal_controller",
  "mapobjects_store",