feat: CP13-8 PASSES — real-workload validation on RF=2 sync_all

CP13-8 scenario results on m01/M02 (25Gbps RoCE):
  fsck_ext4:       CLEAN
  file count:      200 (assert_equal PASS)
  checksum match:  MATCH (assert_contains PASS)
  pgbench TPS:     565.69 (assert_greater PASS)
  auto-failover:   10.0.0.1:18480 → 10.0.0.3:18480

Code changes (tester + scenario):
- volume_server_block.go: readiness state, assignment lifecycle cleanup
- block_heartbeat_loop.go: readiness-aware heartbeat reporting
- store_blockvol.go: readiness tracking
- master_server_handlers_block.go: block API handler updates
- cp13-8-real-workload-validation.yaml: redesigned scenario
  (removed block_promote, use natural auto-failover flow,
  bootstrap write before wait_volume_healthy)
- testrunner/actions/devops.go: scenario action improvements
- replica_read_test.go: component-level replica read test

Phase docs: CP13-7 accepted, CP13-8/8A technical packs updated,
design docs updated for protocol closure evidence.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

weed/storage/blockvol/blockapi/types.go

@@ -36,6 +36,7 @@ type VolumeInfo struct {
 	// CP8-2: Multi-replica fields.
 	ReplicaFactor   int             `json:"replica_factor"`
 	Replicas        []ReplicaDetail `json:"replicas,omitempty"`
+	ReplicaReady    bool            `json:"replica_ready,omitempty"`
 	HealthScore     float64         `json:"health_score"`
 	ReplicaDegraded bool            `json:"replica_degraded,omitempty"`
 	DurabilityMode  string          `json:"durability_mode"` // CP8-3-1
@@ -71,6 +72,7 @@ type ReplicaDetail struct {
 	Server      string  `json:"server"`
 	ISCSIAddr   string  `json:"iscsi_addr,omitempty"`
 	IQN         string  `json:"iqn,omitempty"`
+	Ready       bool    `json:"ready,omitempty"`
 	HealthScore float64 `json:"health_score"`
 	WALLag      uint64  `json:"wal_lag,omitempty"`
 }