[AZ-683] scan_controller POI queue + 5/min cap + decision window

Adds the prioritized POI queue on top of the AZ-682 FSM substrate:
priority = confidence x proximity x age_factor; rolling 60s window
caps surfaces at 5; confidence-scaled decision window (40% -> 30s,
100% -> 120s, linear; <40% never surfaces); tick() runs the timeout
sweep and silently forgets expired POIs (no IgnoredItem per spec);
DeclinePoi via operator command returns a DeclineAction for AZ-685
to persist.

ScanControllerHandle gains submit_poi_candidate /
next_poi_for_surface / decline_poi / poi_queue_len /
pois_in_window. submit_operator_cmd return type widens from
Result<()> to Result<SubmitOutcome>. ScanMetrics and health()
surface queue depth and counters.

Tests: 26 unit + 11 integration in scan_controller (all AC1..AC5 +
DeclinePoi end-to-end). Workspace clippy on scan_controller clean.
Pre-existing autopilot::Runtime::vlm_provider_name dead-code error
from batch 4 still open (see cumulative C5).

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

_docs/_autodev_state.md

@@ -6,9 +6,9 @@ step: 7
 name: Implement
 status: in_progress
 sub_step:
-  phase: 20
+  phase: 23
   name: tracker-update-in-testing
-  detail: "batch 12 (AZ-657 + AZ-682) implemented and reviewed; awaiting commit + In Testing"
+  detail: "batch 13 (AZ-683) implemented and reviewed; awaiting commit + In Testing"
 retry_count: 0
 cycle: 1
 tracker: jira