docs(bf-28dv): verify Component 24 already implemented

notes/bf-28dv.md

@@ -0,0 +1,48 @@
+# Component 24 Verification: Fleet-level Sentinel Link Coordination
+
+## Status: Already Implemented
+
+Component 24 (Fleet-level sentinel link coordination) was already fully implemented in `ratecontrol.go` at the time this bead was created.
+
+## Verified Implementation
+
+All requirements from the plan are present:
+
+1. **Zone-level idle detection with sentinel designation**
+   - Function: `designateSentinel()` (line 291)
+   - Designates lexicographically smallest MAC as sentinel
+   - Sentinel runs at 5 Hz (RateSentinel), others at 1 Hz (RateFleetIdle)
+   - Test: `TestZoneIdleDetectionAndSentinelDesignation`
+
+2. **Fleet-wide idle state tracking**
+   - Field: `fleetIdle bool` (line 63)
+   - Set when all zones are idle (line 285): `rc.fleetIdle = allZonesIdle && len(rc.zones) > 0`
+   - Test: `TestFleetIdleDetection`
+
+3. **Prediction engine preemptive zone ramping**
+   - Method: `RampZone(zoneID string, rampAdjacent bool)` (line 189)
+   - Ramps all nodes in zone to active rate (50 Hz)
+   - Optionally ramps adjacent zones to sentinel (5 Hz)
+   - Test: `TestRampZonePredictionEngine`
+
+4. **1 Hz floor rate for fully-idle fleet**
+   - Constant: `RateFleetIdle = 1` (line 19)
+   - Applied to non-sentinel nodes in `designateSentinel()` (line 308)
+
+## Tests Passing
+
+All 15 ratecontrol tests pass, including:
+- Zone-aware idle detection and sentinel designation
+- Fleet idle state tracking
+- Adjacent zone ramping on activation
+- Prediction engine RampZone method
+- Sentinel redesignation on node disconnect
+
+## Implementation Date
+
+The commit history shows this was implemented in commit `9c36b0d`:
+```
+feat(bf-28dv): implement zone-aware rate control (Component 24)
+```
+
+This bead serves as documentation that Component 24 is complete.