Gate a release plan's first machine and roll a failed build back there (hq ADR 0236)

A build that reported applied was sent everywhere; one that then did nothing, served
no tools or broke its machine's word reached every machine. Now the first machine is
judged by the component's health (the core's definitions, as doctor probes H-*, or a
module's own) three times over two minutes within ten; a failing gate puts the previous
build back there once, marks the build, and says it as a condition and an event.
Upgrades roll out by default; the bus is a planned step; a module deleted at its
source is not built (the public-acme plan failure).

internal/broker/streams.go

@@ -213,7 +213,9 @@ var ControllerStates = []string{"applied", "refused", "built-before",
 	"secret-replaced",
 	// And every act a healer takes on a condition (novox/hq to-be 45 §7, Phase 3): a repair the mesh
 	// made by itself is said like one a person made, never quietly.
-	"healer-acted"}
+	"healer-acted",
+	// And a build put back after its gate failed on its first machine (novox/hq ADR 0235, to-be 45 §8).
+	"rolled-back"}
 
 // BusAdvisories are what the bus server says about the mesh's own account that the controller
 // reads (novox/hq to-be 45 §3, S9): a durable consumer that handed a message over as often as it