feat(office): mail preview, infinite scroll, pane resize, and scrollbars

Polish the office TUI with proportional pane layout, drag resize, live
filtering, HTML mail preview, paginated mail lists, overflow scrollbars,
flattened navigation, and project save/status fixes; add UpdateProjectStatus.

Co-authored-by: Cursor <cursoragent@cursor.com>

cmd/office/model/calendar_display.go

@@ -0,0 +1,40 @@
+package model
+
+import "fmt"
+
+// ClassifyCalendarRow decides whether an API row is a calendar or an event.
+func ClassifyCalendarRow(raw map[string]any) (Kind, string) {
+	if raw == nil {
+		return KindCalendar, "Calendar"
+	}
+	if strRaw(raw, "start") != "" || strRaw(raw, "end") != "" {
+		return KindEvent, "Event"
+	}
+	if strRaw(raw, "eventType") != "" {
+		return KindEvent, "Event"
+	}
+	return KindCalendar, "Calendar"
+}
+
+// CalendarTypeLabel returns the type column text for a calendar list row.
+func CalendarTypeLabel(it Item) string {
+	if it.Raw != nil {
+		if t := strRaw(it.Raw, "type"); t != "" {
+			return t
+		}
+	}
+	_, label := ClassifyCalendarRow(it.Raw)
+	return label
+}
+
+// FormatCalendarDateTime formats start/end timestamps for the calendar table.
+func FormatCalendarDateTime(v any) string {
+	t, ok := parseDeadlineTime(v)
+	if !ok {
+		if s := fmt.Sprint(v); s != "" && s != "<nil>" {
+			return s
+		}
+		return ""
+	}
+	return t.Format("Jan 2 15:04")
+}