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_test.go

@@ -0,0 +1,37 @@
+package model
+
+import "testing"
+
+func TestClassifyCalendarRow(t *testing.T) {
+	kind, label := ClassifyCalendarRow(map[string]any{
+		"title": "Standup",
+		"start": "2026-06-24T10:00:00Z",
+	})
+	if kind != KindEvent || label != "Event" {
+		t.Fatalf("got kind=%s label=%q", kind, label)
+	}
+	kind, label = ClassifyCalendarRow(map[string]any{"title": "Work"})
+	if kind != KindCalendar || label != "Calendar" {
+		t.Fatalf("got kind=%s label=%q", kind, label)
+	}
+}
+
+func TestBuildCalendarColumnsIncludesType(t *testing.T) {
+	items := []Item{{
+		ID: "1", Title: "Meet", Kind: KindEvent,
+		Raw: map[string]any{"type": "Event", "start": "2026-06-24T10:00:00Z"},
+	}}
+	cols := BuildColumns(SubjectCalendar, items)
+	found := false
+	for _, c := range cols {
+		if c.Key == "type" {
+			found = true
+		}
+		if c.Key == "subtitle" {
+			t.Fatal("subtitle column should not appear")
+		}
+	}
+	if !found {
+		t.Fatal("expected type column")
+	}
+}