controller: fix-3 dead-app alerting + fix-6 ring cap/spill/spam (WIP, pre-build)

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017CDMFpFx84pfviCTVuGGhf

controller/internal/stacks/downstate_test.go

@@ -0,0 +1,23 @@
+package stacks
+
+import "testing"
+
+// fix-3: only stopped/exited count as "down" for a deployed app. starting/unhealthy (running),
+// restarting/deploying (transient), paused (deliberate), unknown (ambiguous) must NOT alert.
+func TestIsDownState(t *testing.T) {
+	down := []ContainerState{StateStopped, StateExited}
+	for _, s := range down {
+		if !IsDownState(s) {
+			t.Errorf("IsDownState(%q) = false, want true", s)
+		}
+	}
+	notDown := []ContainerState{
+		StateRunning, StateStarting, StateUnhealthy, StateRestarting,
+		StateDeploying, StatePaused, StateUnknown, StateNotDeployed, StateOrphaned,
+	}
+	for _, s := range notDown {
+		if IsDownState(s) {
+			t.Errorf("IsDownState(%q) = true, want false (must not manufacture a dead-app alert)", s)
+		}
+	}
+}