ENG-10 sdk: a routed image says the seat it came through and that seat's holder (design 51)

declaration.Container gains ImageSeat and ImageHolder, catalogue.Rendering SeatHolder, for the node-engine to retry a
failed pull on the holder's settled (A7's request R1).

Claude-Session: https://claude.ai/code/session_01JG73KJNrH5EgFXMKKYSrig

go/catalogue/declaration.go

@@ -238,6 +238,11 @@ type Rendering struct {
 	// when no holder is reachable yet; see seat_into.go for which seats are answered.
 	SeatReach map[string]string
 
+	// SeatHolder is the module holding each seat SeatReach answers, by seat, from the holdings the composition has (novox/hq
+	// design 51, issue 1966 ENG-10): written beside an image routed through the seat, for the node-engine to wait on when its
+	// pull fails. Absent for a seat with no holder on record.
+	SeatHolder map[string]string
+
 	// Built is every `<module>/<artifact>` the mesh has built. What tells a reference recorded
 	// with an address — before references were kept without one — from an image a module runs
 	// straight from a public registry.

go/declaration/declaration.go

@@ -1368,8 +1368,14 @@ type Container struct {
 	Module string `json:"module,omitempty"`
 	Name   string `json:"name"`
 	// Image is pinned by digest (novox/hq ADR 0006) — a tag moves and a digest does not.
-	Image string            `json:"image"`
-	Env   map[string]string `json:"env,omitempty"`
+	Image string `json:"image"`
+	// ImageSeat and ImageHolder say, beside an image the composition routed through a store, the seat the reference came
+	// through and that seat's holder (novox/hq design 51, issue 1966 ENG-10): what the node-engine finds the holder to wait
+	// on when the pull fails. Not part of what a container is: they are no part of its spec or digest, so a declaration
+	// composed again for a new holder replaces no container.
+	ImageSeat   string            `json:"image-seat,omitempty"`
+	ImageHolder string            `json:"image-holder,omitempty"`
+	Env         map[string]string `json:"env,omitempty"`
 	// EnvFile names files the runtime reads environment from, in order.
 	//
 	// **Because a secret may not travel in Env.** A declaration reaches a node over the broker,