Announce every state another module reads as readable, and refuse a catalogue that does not (issue 774)

The controller grants a read only from the owner's announcement (ADR 0495 clause 3). gitea announced `bound`
unreadable, so mesh-provisioner bound no forge account; disk-load announced `readings` unreadable, refused to restic,
nfs-server and mounts; restic announced `good` unreadable, which the self-check reads. Nothing in the catalogue
compared readers with announcements since the gate's manifest check went (clause 5).

Quick fix: mark those three states readable. Thorough fix: also checks/readable, which reads every owner's Go and
TypeScript announcement and refuses any `reads` of a state it does not announce readable, so the next owner to
announce cannot repeat it. Chose thorough: the same kind hit three owners at once.
Reads of other repositories' owners (mesh-controller.lease, mesh-grants.accounts) are not judged here.

modules/disk-load/cmd/disk-load/main.go

@@ -24,7 +24,8 @@ import (
 func logf(format string, args ...any) { fmt.Fprintf(os.Stderr, "[disk-load] "+format+"\n", args...) }
 
 func main() {
-	if err := stdio.Keeps(announce.State{Name: StateReadings}); err != nil {
+	// Readable: restic, nfs-server, mounts and the self-check read it (their manifests' `reads`); checks/readable holds it.
+	if err := stdio.Keeps(announce.State{Name: StateReadings, Readable: true}); err != nil {
 		logf("%v", err)
 		os.Exit(1)
 	}