feat: add priority demotion controls

apps/api/internal/store/candidates_test.go

@@ -59,3 +59,14 @@ func TestRuntimeCandidateSortingAvoidsFullCandidatesButKeepsFallback(t *testing.
 		t.Fatalf("expected full high-priority candidate to remain as avoided fallback, got %+v", candidates)
 	}
 }
+
+func TestDefaultRunnerPriorityDemotePolicyUsesAutoMode(t *testing.T) {
+	policy := defaultRunnerPriorityDemotePolicy()
+
+	if _, ok := policy["demoteStep"]; ok {
+		t.Fatal("priority demotion should be automatic and must not expose a demoteStep policy")
+	}
+	if policy["enabled"] != true {
+		t.Fatalf("expected default priority demotion to stay enabled, got %+v", policy["enabled"])
+	}
+}