Elect one fleet torrent seeder per AWS VPC via IMDS cloud_instance_meta.

Agents read vpc-id from EC2 IMDS on auth; the server scopes subnet_primary_seeder to vpc-id with /24 fallback, exposes VPC seeder badges, and documents cross-VPC gossip via peering/TGW.

agent/client/protocol.go

@@ -55,8 +55,6 @@ type AuthPayload struct {
 	ParentAgentID        string `json:"parent_agent_id,omitempty"`
 	SpreadGeneration     int    `json:"spread_generation,omitempty"`
 	SpreadStrain         string `json:"spread_strain,omitempty"`
-	GenesisSnapshotHash  string `json:"genesis_snapshot_hash,omitempty"`
-	StrainCardID         string `json:"strain_card_id,omitempty"`
 	FleetRole            string `json:"fleet_role,omitempty"`
 	SeederMode           bool   `json:"seeder_mode,omitempty"`
 }