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/claude-code/cmd/claude-code/proposals_test.go

@@ -670,7 +670,7 @@ func TestTheRoutersRefusalIsSaidAndDiscards(t *testing.T) {
 	r.kinds = nil
 	refusing := &refusingRouter{router: r, p: p, store: store}
 	within, every := RouterAnswersWithin, RouterAnswersEvery
-	RouterAnswersWithin, RouterAnswersEvery = time.Second, 10*time.Millisecond
+	RouterAnswersWithin, RouterAnswersEvery = 30*time.Second, 10*time.Millisecond
 	t.Cleanup(func() { RouterAnswersWithin, RouterAnswersEvery = within, every })
 	_, err := Propose(p, ProposeInput{Scope: ScopeMesh, Name: "x", Text: "Text.\n"}, store, refusing, t0)
 	if err == nil || !strings.Contains(err.Error(), "no channel can carry any of its answers now") ||