phraser: name the service that is down (V-444)

Stub and LLM paths both read loop.DownServices, so the message can never name
a service the predicate did not fire on. Two down at once are both named — he
needs the blast radius.

internal/phraser/phraser_test.go

@@ -78,12 +78,14 @@ func TestPhraseNudgeBreakDeskDuration(t *testing.T) {
 }
 
 func TestPhraseNudgeServiceDownNamedService(t *testing.T) {
-	// a service_down fact whose Key is the specific service name → the phrase
-	// names the service, not just "service down".
+	// one fact per kuma monitor → the phrase names the monitor that is down.
 	now := time.Now().UTC()
 	st := loop.State{
-		Now:   now,
-		Facts: map[string]store.Fact{"service_down": {Key: "nginx", Ts: now, Source: "poll:healthcheck", Value: `"down"`}},
+		Now: now,
+		Facts: map[string]store.Fact{
+			"service_down:nginx": {Key: "service_down:nginx", Ts: now, Source: loop.ServiceDownSource, Value: `"down"`},
+			"service_down:db":    {Key: "service_down:db", Ts: now, Source: loop.ServiceDownSource, Value: `"up"`},
+		},
 	}
 	c := loop.Candidate{Rule: loop.ServiceDownRule(), Severity: loop.Sev4, State: st}
 	pn, _ := NewStub().PhraseNudge(context.Background(), c)
@@ -96,12 +98,12 @@ func TestPhraseNudgeServiceDownNamedService(t *testing.T) {
 }
 
 func TestPhraseNudgeServiceDownGenericKey(t *testing.T) {
-	// the rule key itself ("service_down") rather than a specific service →
-	// the generic phrase, not a phantom "service_down down on homesrv".
+	// the old aggregate key, still in the store from before the per-monitor
+	// facts landed → the generic phrase, never a phantom "service_down down".
 	now := time.Now().UTC()
 	st := loop.State{
 		Now:   now,
-		Facts: map[string]store.Fact{"service_down": {Key: "service_down", Ts: now, Source: "poll:healthcheck", Value: `"down"`}},
+		Facts: map[string]store.Fact{"service_down": {Key: "service_down", Ts: now, Source: loop.ServiceDownSource, Value: `"down"`}},
 	}
 	c := loop.Candidate{Rule: loop.ServiceDownRule(), Severity: loop.Sev4, State: st}
 	pn, _ := NewStub().PhraseNudge(context.Background(), c)
@@ -110,6 +112,26 @@ func TestPhraseNudgeServiceDownGenericKey(t *testing.T) {
 	}
 }
 
+// Two monitors down at once must both be named — he needs to know the blast
+// radius, and "a service is down" was the whole defect being fixed here.
+func TestPhraseNudgeServiceDownNamesEveryDownMonitor(t *testing.T) {
+	now := time.Now().UTC()
+	st := loop.State{
+		Now: now,
+		Facts: map[string]store.Fact{
+			"service_down:nginx": {Key: "service_down:nginx", Ts: now, Source: loop.ServiceDownSource, Value: `"down"`},
+			"service_down:db":    {Key: "service_down:db", Ts: now, Source: loop.ServiceDownSource, Value: `"down"`},
+		},
+	}
+	c := loop.Candidate{Rule: loop.ServiceDownRule(), Severity: loop.Sev4, State: st}
+	pn, _ := NewStub().PhraseNudge(context.Background(), c)
+	for _, want := range []string{"nginx", "db"} {
+		if !strings.Contains(pn.Body, want) {
+			t.Fatalf("body should name %q, got %q", want, pn.Body)
+		}
+	}
+}
+
 func TestPhraseNudgeUnknownRuleFallsBack(t *testing.T) {
 	// a rule without a dedicated template — generic fallback names the rule +
 	// severity gist. never empty.