Make tests that wait for concurrent work wait on the event or a condition with a long deadline (issue 1814)

A test that slept a fixed time and then asserted what a goroutine, process or
watcher did failed under the checker's load. Each now waits for its positive
evidence (a started baseline, a call counted, a state reached) within 30 s, and
the concurrency-limit tests meet at a barrier instead of overlapping by sleep.

Claude-Session: https://claude.ai/code/session_01NcbgfJ9Gum47zkFKWRaovL

modules/messenger/cmd/messenger/answers_test.go

@@ -882,7 +882,7 @@ func TestBreakGlassIsAFileRootMadeAndTheMinuteGoesOn(t *testing.T) {
 		go func() { h.Tick(); close(done) }()
 		select {
 		case <-done:
-		case <-time.After(5 * time.Second):
+		case <-time.After(30 * time.Second):
 			t.Fatal("the router's minute hung on a break-glass file")
 		}
 	}

modules/messenger/cmd/messenger/review_test.go

@@ -552,7 +552,7 @@ func TestTheRootFreeWordIsNotAskedWhileTheWorkIsHeld(t *testing.T) {
 	}()
 	select {
 	case <-linked:
-	case <-time.After(2 * time.Second):
+	case <-time.After(30 * time.Second):
 		close(slow)
 		t.Fatal("a link waited for the controller's root-free word: the work was held while it was asked")
 	}