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/mesh-vault/cmd/mesh-vault/core_test.go

@@ -175,7 +175,7 @@ authorization {
 	controller := connectAs(t, url, "controller")
 	ask = func(name, key string) (Answer, error) {
 		raw, _ := json.Marshal(map[string]string{"name": name, "public_key": key})
-		msg, err := controller.Request("mesh.seat.mesh-vault.call.get.controller", raw, 3*time.Second)
+		msg, err := controller.Request("mesh.seat.mesh-vault.call.get.controller", raw, 30*time.Second)
 		if err != nil {
 			return Answer{}, err
 		}

modules/mesh-vault/cmd/mesh-vault/nodekey_test.go

@@ -170,7 +170,7 @@ func TestOnARealBusANodeEngineStatesOnlyItsOwnKey(t *testing.T) {
 
 	call := func(user, subject string, args any) (json.RawMessage, error) {
 		raw, _ := json.Marshal(args)
-		msg, err := connectAs(t, s.ClientURL(), user).Request(subject, raw, 3*time.Second)
+		msg, err := connectAs(t, s.ClientURL(), user).Request(subject, raw, 30*time.Second)
 		if err != nil {
 			return nil, err
 		}