Let a module declare a log the controller creates and never removes (ADR 0297)

The issue tracker's history lasts seven days on the events stream and its
bucket fills toward a cap with no warning (issues 501, 502). A module may
now declare `logs`; the controller creates each as a stream on the bus
(create-or-update, never deleted or recreated, reported when undeclared),
issues it to the owner's assignments in their membership, grants the
runtime exactly the append and direct-read subjects, and raises a
condition when any module's bucket or log reaches 75% of its cap, cleared
below 70%.

internal/broker/users.go

@@ -35,6 +35,8 @@ type Declared struct {
 	Invokes []string
 	// State is the state it keeps, each a bucket its instances write (novox/hq ADR 0201).
 	State []Bucket
+	// Logs are the logs it keeps, each a stream its instances append to (novox/hq ADR 0297).
+	Logs []Log
 	// Reads are other modules' state it reads, each `<module>.<name>` (novox/hq ADR 0201).
 	Reads []string
 	// KeyedReads are keys of other modules' state it reads, each one key alone: what a seat's holder is
@@ -124,6 +126,7 @@ func Users(r Records) ([]Principal, error) {
 				Holds: d.Holds, Uses: d.Uses, Watches: d.Watches, Invokes: d.Invokes,
 				State: stateNames(d.State), Reads: d.Reads, SnapshotsTheBus: d.SnapshotsTheBus,
 				PerMachine: perMachineNames(d.State), KeyedReads: d.KeyedReads,
+				Logs: logNames(d.Logs),
 			})
 		}
 		if runtimeHere {