Seats keep their former names, so a rename breaks nothing (ADR 0122, phase 2)

Phase 1 made the set data; a rename still broke every reference to the old
name. This adds the stable identity: a seat's canonical name changes and its
old name becomes an alias that resolves to it forever. SeatNamed and the holder
and display matching resolve a name (former or current) to its seat, so a
manifest's claim, a held record, the git-seat lookup and the build machine's
embedded set all go on working unchanged after a rename. seat_alias table
(migration 0035), inventory Aliases/RenameSeat, openInventory loads them, and a
'seat rename <from> <to>' command does the whole thing — one operation, no
rebuild, no re-registration, no freeze. Behaviour-neutral until a seat is
renamed. Validated against postgres.

internal/catalogue/seats.go

@@ -94,18 +94,36 @@ func UseSeats(s []Seat) {
 	}
 }
 
+// aliases maps a seat's former names to its current canonical name (novox/hq ADR 0122). Loaded from
+// the store alongside the set, so a reference to a name a seat used to have — a manifest's claim, a
+// held record — still resolves to it after a rename, and nothing downstream has to change.
+var aliases = map[string]string{}
+
+// UseAliases replaces the former-name map with the one the control plane read from its store. Empty
+// is fine and ordinary: a mesh whose seats have never been renamed has no aliases.
+func UseAliases(m map[string]string) { aliases = m }
+
 // Seats is every seat the mesh defines, in reading order.
 func Seats() []Seat {
 	return append([]Seat(nil), seats...)
 }
 
-// SeatNamed is the seat a claim names, if the mesh defines one.
+// SeatNamed is the seat a name refers to, whether that is its current name or one it used to have
+// (novox/hq ADR 0122). A former name resolves to the seat's canonical row, so a rename breaks no
+// reference to the old name.
 func SeatNamed(name string) (Seat, bool) {
 	for _, s := range seats {
 		if s.Name == name {
 			return s, true
 		}
 	}
+	if canonical, aliased := aliases[name]; aliased {
+		for _, s := range seats {
+			if s.Name == canonical {
+				return s, true
+			}
+		}
+	}
 	return Seat{}, false
 }
 
@@ -211,7 +229,10 @@ func HolderAmong(provision string, providers []Provider, held []Held) (Provider,
 		return Provider{}, false
 	}
 	for _, h := range held {
-		if h.Claim != seat.Name || h.Scope != seat.Scope {
+		// Resolve the held claim to a seat rather than comparing names, so a record naming a seat's
+		// former name still matches it after a rename (novox/hq ADR 0122).
+		hs, ok := SeatNamed(h.Claim)
+		if !ok || hs.Name != seat.Name || h.Scope != seat.Scope {
 			continue
 		}
 		for _, p := range providers {