Phase 6: fix the live Home Assistant write (Local Calendar, no event id)

The first live run against the new calendar.school entity failed loudly twice,
and both causes are fixed here.

- The Local Calendar rejects `return_response` on calendar.create_event. The
  client retries the call without it and ignores the changed-states array that
  Home Assistant returns instead.
- Home Assistant then reports no event id. The item keeps the description
  marker ([compass-nhs:<id>]) as its reference, so it leaves the candidate set
  and is never written twice. The live retry proved it: both events already in
  the calendar were adopted by their markers, with no duplicate.
- calendar.get_events reports `start` / `end` (a date-time or a bare date), not
  `start_date_time`; the reader now accepts all three shapes.

A model must no longer classify events. The calendar write depends on the
school-event rule, and the LLM labelled every event "normal"; events now keep
the deterministic rule under both classifiers.

Also fix the Phase 5 screenshot script: the calendar banner shares the `.scan`
class, so select each banner by its labelled section.

Docs record the accepted decision: Sam chose a Home Assistant Local Calendar,
so the target is calendar.school.

Co-Authored-By: Paperclip <noreply@paperclip.ing>

internal/calendar/ha_test.go

@@ -18,15 +18,16 @@ import (
 type fakeHA struct {
 	*httptest.Server
 
-	mu          sync.Mutex
-	entity      string
-	events      []map[string]any
-	createCalls int
-	getCalls    int
-	failCreate  bool
-	returnUID   bool
-	lastCreate  map[string]any
-	lastGet     map[string]any
+	mu                   sync.Mutex
+	entity               string
+	events               []map[string]any
+	createCalls          int
+	getCalls             int
+	failCreate           bool
+	returnUID            bool
+	rejectReturnResponse bool
+	lastCreate           map[string]any
+	lastGet              map[string]any
 }
 
 func newFakeHA(t *testing.T, entity string) *fakeHA {
@@ -57,6 +58,14 @@ func newFakeHA(t *testing.T, entity string) *fakeHA {
 		if !f.authOK(w, r) {
 			return
 		}
+		if f.rejectReturnResponse && r.URL.Query().Has("return_response") {
+			w.WriteHeader(http.StatusBadRequest)
+			writeJSON(w, map[string]any{"error": map[string]any{
+				"code":    "unknown_error",
+				"message": "Service does not support responses. Remove return_response from request.",
+			}})
+			return
+		}
 		var body map[string]any
 		if err := json.NewDecoder(r.Body).Decode(&body); err != nil {
 			http.Error(w, "bad json", http.StatusBadRequest)
@@ -76,12 +85,17 @@ func newFakeHA(t *testing.T, entity string) *fakeHA {
 			uid = "uid-" + str(body["summary"])
 		}
 		f.events = append(f.events, map[string]any{
-			"uid":             uid,
-			"summary":         body["summary"],
-			"description":     body["description"],
-			"start_date_time": body["start_date_time"],
-			"end_date_time":   body["end_date_time"],
+			"uid":         uid,
+			"summary":     body["summary"],
+			"description": body["description"],
+			"start":       body["start_date_time"],
+			"end":         body["end_date_time"],
 		})
+		if !r.URL.Query().Has("return_response") {
+			// Home Assistant replies with the changed states, a JSON array.
+			writeJSON(w, []map[string]any{})
+			return
+		}
 		writeJSON(w, map[string]any{
 			"changed_entities": map[string]any{},
 			"service_response": map[string]any{f.entity: map[string]any{"uid": uid}},
@@ -309,3 +323,52 @@ func TestFindMarker(t *testing.T) {
 		}
 	}
 }
+
+// TestCreateEventFallsBackWhenTheCalendarHasNoResponses proves the Local
+// Calendar integration is usable: it rejects `return_response`, which is not a
+// write failure.
+func TestCreateEventFallsBackWhenTheCalendarHasNoResponses(t *testing.T) {
+	ha := newFakeHA(t, "calendar.school")
+	ha.rejectReturnResponse = true
+	c := testClient(t, ha.URL, "calendar.school")
+
+	start := time.Date(2026, 10, 15, 18, 0, 0, 0, time.UTC)
+	uid, err := c.CreateEvent(context.Background(), Event{
+		Summary: "Concert", Start: &start, End: ptrTime(start.Add(time.Hour)),
+		Description: "source: " + Marker(29),
+	})
+	if err != nil {
+		t.Fatalf("CreateEvent: %v", err)
+	}
+	if uid != "" {
+		t.Errorf("want no uid, got %q", uid)
+	}
+	if ha.created() != 1 {
+		t.Fatalf("event was not written (%d create calls)", ha.created())
+	}
+}
+
+// TestParseHATime covers the shapes calendar.get_events reports.
+func TestParseHATime(t *testing.T) {
+	timed := map[string]any{"start": "2026-10-15T15:05:00+11:00"}
+	got, raw := parseHATime(timed, "start")
+	if got == nil || raw != "2026-10-15T15:05:00+11:00" {
+		t.Fatalf("timed = %v %q", got, raw)
+	}
+	if got.Hour() != 15 || got.Minute() != 5 {
+		t.Errorf("timed = %v", got)
+	}
+
+	allDay := map[string]any{"start": "2026-10-15"}
+	got, raw = parseHATime(allDay, "start")
+	if got == nil || raw != "2026-10-15" {
+		t.Fatalf("all-day = %v %q", got, raw)
+	}
+	if y, m, d := got.Date(); y != 2026 || m != time.October || d != 15 {
+		t.Errorf("all-day = %v", got)
+	}
+
+	if got, raw := parseHATime(map[string]any{}, "start"); got != nil || raw != "" {
+		t.Errorf("missing = %v %q", got, raw)
+	}
+}