feat: start Phase 14 V2 core shell

Make the first V2 core owner explicit in sw-block by freezing Phase 14 docs, mode/readiness/publication semantics, and bounded command emission rules. This turns accepted Phase 13 constraints into executable core behavior without overclaiming live runtime cutover.

Made-with: Cursor

sw-block/engine/replication/command.go

@@ -0,0 +1,42 @@
+package replication
+
+// Command is one side-effect-free decision emitted by the Phase 14 core skeleton.
+// Adapters execute commands later; the core only decides them.
+type Command interface {
+	commandName() string
+}
+
+type ApplyRoleCommand struct {
+	VolumeID string
+	Epoch    uint64
+	Role     VolumeRole
+}
+
+func (ApplyRoleCommand) commandName() string { return "apply_role" }
+
+type StartReceiverCommand struct {
+	VolumeID string
+}
+
+func (StartReceiverCommand) commandName() string { return "start_receiver" }
+
+type ConfigureShipperCommand struct {
+	VolumeID string
+	Replicas []ReplicaAssignment
+}
+
+func (ConfigureShipperCommand) commandName() string { return "configure_shipper" }
+
+type InvalidateSessionCommand struct {
+	VolumeID string
+	Reason   string
+}
+
+func (InvalidateSessionCommand) commandName() string { return "invalidate_session" }
+
+type PublishProjectionCommand struct {
+	VolumeID   string
+	Projection PublicationProjection
+}
+
+func (PublishProjectionCommand) commandName() string { return "publish_projection" }