SDK-9: mesh-sdk takes no new seat-specific name (ADR 0613 §5, design 26 *Contracts modules*)

Every seat constant of mesh-sdk is mesh-contracts' generated name; the four whole seats' (BrokerSeat, CheckerSeat,
asks.Seat, buscompose.VaultSeat) are marked deprecated for their importers. The package walk of mesh-sdk's own check
refuses a string literal naming a defined seat or its subjects, and an exported name given to one, beyond
testdata/seat-names.txt, which lists what stands before the move (module names that equal a seat's among them) and
only shrinks. No new test function.

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

go/testdata/seat-names.txt

@@ -0,0 +1,61 @@
+asks/asks.go: Seat
+buscompose/health_grants.go: mesh.seat.mesh-self-check.event.
+buscompose/users.go: VaultSeat
+catalogue/artifact_sweep_seat.go: ArtifactSweepSeat
+catalogue/catalog_seat.go: CatalogSeat
+catalogue/checker_seat.go: CheckerSeat
+catalogue/control_records_seats.go: HandActsSeat
+catalogue/control_records_seats.go: WantsSeat
+catalogue/delivery_seat.go: DeliverySeat
+catalogue/engine_seat.go: EngineSeat
+catalogue/enrolment_seat.go: EnrolmentSeat
+catalogue/environment_into.go: EnvironmentSeat
+catalogue/environment_into.go: LoginShellSeat
+catalogue/environment_into.go: PowerSeat
+catalogue/files.go: FilesSeat
+catalogue/graphical_session.go: BarSeat
+catalogue/graphical_session.go: ClipboardSeat
+catalogue/graphical_session.go: CompositorSeat
+catalogue/graphical_session.go: DisplayServerSeat
+catalogue/graphical_session.go: DisplaySessionSeat
+catalogue/graphical_session.go: LauncherSeat
+catalogue/graphical_session.go: LockScreenSeat
+catalogue/graphical_session.go: LoginManagerSeat
+catalogue/graphical_session.go: NotifierSeat
+catalogue/graphical_session.go: SecretServiceSeat
+catalogue/graphical_session.go: TerminalEmulatorSeat
+catalogue/health_seats.go: ConditionsSeat
+catalogue/health_seats.go: HealersSeat
+catalogue/health_seats.go: SelfCheckSeat
+catalogue/health_seats.go: WatchdogsSeat
+catalogue/node_resolver.go: ResolverSeat
+catalogue/placement_seat.go: PlacementSeat
+catalogue/reads.go: ReadsSeat
+catalogue/seat_contributions.go: BackupSeat
+catalogue/seat_contributions.go: HotkeysSeat
+catalogue/seat_contributions.go: MessageBusSeat
+catalogue/seat_dependencies.go: ContainerRuntimeSeat
+catalogue/seat_dependencies.go: PackageManagerSeat
+catalogue/seat_dependencies.go: ServiceManagerSeat
+catalogue/seats.go: BrokerSeat
+catalogue/shares.go: MountsSeat
+catalogue/shares.go: NFSServerSeat
+delivery/checker.go: mesh-delivery-checker
+delivery/composed.go: mesh-provisioner
+delivery/held.go: mesh.seat.mesh-artifact-sweep.event.
+delivery/placement.go: mesh-self-check
+delivery/provided.go: the-private-network
+delivery/signers.go: mesh-vault
+delivery/stepasks.go: node-build-node
+handacts/handacts.go: mesh-hand-acts
+handacts/handacts.go: Seat
+health/findings.go: KeeperSeat
+health/findings.go: mesh-conditions
+health/findings.go: mesh-healers
+health/findings.go: mesh-self-check
+health/findings.go: SelfCheckSeat
+internal/beside/beside.go: mesh-catalog
+overlay/overlay.go: the-private-network
+provisions/provisions.go: mesh-provisioner
+provisions/provisions.go: mesh-vault
+provisions/provisions.go: Seat