Add server subnet discovery store, API, and agent policy push.

server/internal/api/server_policy.go

@@ -28,6 +28,8 @@ type ServerPolicy struct {
 	ErasureLanesEnabled bool
 	// FleetTorrentEnabled enables fleet-wide shard DHT gossip and torrent manifests.
 	FleetTorrentEnabled bool
+	SubnetReconEnabled     bool
+	SubnetReconIntervalMin int
 	// StrainHospiceWinRateThreshold auto-retires strains below this win rate when AI control is on.
 	StrainHospiceWinRateThreshold float64
 	// StrainHospiceMinAttempts is minimum spread outcomes before AI auto-hospice applies.