distribution's program listens on 5100 and the registry container on 5001, so no mapping names the store's port

The composer finds a listen's machine port in a container mapping that names
it on either side (MachineSide). The program's listen 5000 matched the
registry container's inner 5000 in 127.0.0.1:5001:5000, so the store's address
became the container's loopback side and the program's own port was never
opened: the move to 83cd1a3d on 2026-11-08 23:25 UTC cut the artifact store off
(issue 1966 note 109). The program now binds 5100, where every machine fetches
(the artifact-store alias and the seats' reach agree), and the container serves
5001 inside and out. A row holds that no container names 5100.

Undo: revert this commit.

Claude-Session: https://claude.ai/code/session_01NcbgfFSnn24M3GcqttoU7i

modules/distribution/cmd/distribution/main.go

@@ -71,7 +71,7 @@ func run(ctx context.Context, getenv func(string) string) error {
 			d, err := oci.Digest(name, tag)
 			return d != "", err
 		}}
-	srv := &http.Server{Addr: or(getenv("MESH_REGISTRY_LISTEN"), ":5000"), Handler: front, ReadHeaderTimeout: 30 * time.Second}
+	srv := &http.Server{Addr: or(getenv("MESH_REGISTRY_LISTEN"), ":5100"), Handler: front, ReadHeaderTimeout: 30 * time.Second}
 	errs := make(chan error, 1)
 	go func() { errs <- srv.ListenAndServe() }()
 	logger.Printf("serving the store's port %s in front of %s", srv.Addr, store)