One bus: the AMQP transport is gone from the host

The mesh runs on the seat's bus alone (novox/hq ADR 0131, design 28 task 5.5). The host's old
dialling and enrolment paths are deleted with the switch that chose between them; a membership or
a token naming another bus is refused before anything is sent, rather than dialled on a transport
that no longer exists.

internal/link/bus.go

@@ -6,7 +6,6 @@ import (
 	"time"
 
 	"github.com/nats-io/nats.go"
-	amqp "github.com/rabbitmq/amqp091-go"
 )
 
 // Bus is what a host needs of the mesh's bus, in the mesh's own words.
@@ -34,22 +33,6 @@ type Bus interface {
 
 // --- The bus the mesh runs on today -----------------------------------------------------------
 
-// OverCurrent is the bus as a channel, until the rollout.
-type OverCurrent struct{ Channel *amqp.Channel }
-
-func (b OverCurrent) Report(ctx context.Context, node string, body []byte) error {
-	// Mandatory: an unroutable report comes back rather than disappearing.
-	return b.Channel.PublishWithContext(ctx, Exchange, KeyReport, true, false,
-		amqp.Publishing{ContentType: "application/json", Body: body})
-}
-
-func (b OverCurrent) Alive(ctx context.Context, node string, body []byte) error {
-	return b.Channel.PublishWithContext(ctx, Exchange, KeyAlive, false, false,
-		amqp.Publishing{ContentType: "application/json", Body: body})
-}
-
-// --- NATS ---------------------------------------------------------------------------------
-
 // OverNATS is the bus as a connection. A report goes through JetStream because it must survive
 // the controller's store restarting; a heartbeat does not, because it must not.
 type OverNATS struct {