fix(calendar): improve code quality from review

- Patch only attendees array when declining, not full event object
- Add defensive guard in expandRepeatSchedule against infinite loop
- Add JSON output test for propose-time command

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: salmonumbrella

internal/cmd/calendar_propose_time.go

@@ -9,6 +9,8 @@ import (
 	"runtime"
 	"strings"
 
+	"google.golang.org/api/calendar/v3"
+
 	"github.com/steipete/gogcli/internal/outfmt"
 	"github.com/steipete/gogcli/internal/ui"
 )
@@ -90,7 +92,12 @@ func (c *CalendarProposeTimeCmd) Run(ctx context.Context, flags *RootFlags) erro
 			event.Attendees[*selfIdx].Comment = strings.TrimSpace(c.Comment)
 		}
 
-		if _, err := svc.Events.Patch(calendarID, eventID, event).Do(); err != nil {
+		// Create a minimal patch with only attendees to avoid side effects
+		patchEvent := &calendar.Event{
+			Attendees: event.Attendees,
+		}
+
+		if _, err := svc.Events.Patch(calendarID, eventID, patchEvent).Do(); err != nil {
 			return fmt.Errorf("failed to decline event: %w", err)
 		}
 	}

internal/cmd/calendar_propose_time_test.go

@@ -14,6 +14,7 @@ import (
 	"google.golang.org/api/calendar/v3"
 	"google.golang.org/api/option"
 
+	"github.com/steipete/gogcli/internal/outfmt"
 	"github.com/steipete/gogcli/internal/ui"
 )
 
@@ -139,6 +140,89 @@ func TestCalendarProposeTimeCmd_Text(t *testing.T) {
 	}
 }
 
+func TestCalendarProposeTimeCmd_JSON(t *testing.T) {
+	origNew := newCalendarService
+	origOpen := openProposeTimeBrowser
+	t.Cleanup(func() {
+		newCalendarService = origNew
+		openProposeTimeBrowser = origOpen
+	})
+	openProposeTimeBrowser = func(url string) error { return nil }
+
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		path := strings.TrimPrefix(r.URL.Path, "/calendar/v3")
+		if strings.Contains(path, "/calendars/cal1/events/evt1") && r.Method == http.MethodGet {
+			w.Header().Set("Content-Type", "application/json")
+			_ = json.NewEncoder(w).Encode(map[string]any{
+				"id":      "evt1",
+				"summary": "Team Meeting",
+				"start":   map[string]string{"dateTime": "2026-01-16T19:30:00-08:00"},
+				"end":     map[string]string{"dateTime": "2026-01-16T20:30:00-08:00"},
+				"attendees": []map[string]any{
+					{"email": "a@b.com", "self": true},
+					{"email": "organizer@b.com", "organizer": true},
+				},
+			})
+			return
+		}
+		http.NotFound(w, r)
+	}))
+	defer srv.Close()
+
+	svc, err := calendar.NewService(context.Background(),
+		option.WithoutAuthentication(),
+		option.WithHTTPClient(srv.Client()),
+		option.WithEndpoint(srv.URL+"/"),
+	)
+	if err != nil {
+		t.Fatalf("NewService: %v", err)
+	}
+	newCalendarService = func(context.Context, string) (*calendar.Service, error) { return svc, nil }
+
+	flags := &RootFlags{Account: "a@b.com", JSON: true}
+	out := captureStdout(t, func() {
+		u, uiErr := ui.New(ui.Options{Stdout: os.Stdout, Stderr: io.Discard, Color: "never"})
+		if uiErr != nil {
+			t.Fatalf("ui.New: %v", uiErr)
+		}
+		ctx := ui.WithUI(context.Background(), u)
+		ctx = outfmt.WithMode(ctx, outfmt.Mode{JSON: true})
+
+		cmd := &CalendarProposeTimeCmd{}
+		if err := runKong(t, cmd, []string{"cal1", "evt1"}, ctx, flags); err != nil {
+			t.Fatalf("propose-time JSON: %v", err)
+		}
+	})
+
+	// Parse and verify JSON structure
+	var result map[string]any
+	if err := json.Unmarshal([]byte(out), &result); err != nil {
+		t.Fatalf("failed to parse JSON output: %v\noutput: %s", err, out)
+	}
+
+	// Verify required fields
+	requiredFields := []string{"event_id", "calendar_id", "summary", "propose_url", "api_limitation", "issue_tracker_url", "upvote_action", "current_start", "current_end"}
+	for _, field := range requiredFields {
+		if _, ok := result[field]; !ok {
+			t.Errorf("JSON missing required field %q", field)
+		}
+	}
+
+	if result["event_id"] != "evt1" {
+		t.Errorf("event_id = %v, want evt1", result["event_id"])
+	}
+	if result["calendar_id"] != "cal1" {
+		t.Errorf("calendar_id = %v, want cal1", result["calendar_id"])
+	}
+	if result["summary"] != "Team Meeting" {
+		t.Errorf("summary = %v, want Team Meeting", result["summary"])
+	}
+	proposeURL, ok := result["propose_url"].(string)
+	if !ok || !strings.Contains(proposeURL, "proposetime/") {
+		t.Errorf("propose_url invalid: %v", result["propose_url"])
+	}
+}
+
 func TestCalendarProposeTimeCmd_WithDecline(t *testing.T) {
 	origNew := newCalendarService
 	origOpen := openProposeTimeBrowser

internal/cmd/tasks_repeat.go

@@ -65,6 +65,11 @@ func expandRepeatSchedule(start time.Time, unit repeatUnit, count int, until *ti
 	if count < 0 {
 		count = 0
 	}
+	// Defensive guard: if neither count nor until is set, return single occurrence
+	// to prevent infinite loop (caller should validate, but be safe)
+	if count == 0 && until == nil {
+		return []time.Time{start}
+	}
 	out := []time.Time{}
 	for i := 0; ; i++ {
 		t := addRepeat(start, unit, i)