feat(office): table detail panes and Alt+1/2/3 layout toggles

Add spreadsheet-style list, split detail pane with forms and document preview,
and Alt+1/2/3 to show/hide panes with even width distribution.

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

cmd/office/model/columns_test.go

@@ -0,0 +1,55 @@
+package model
+
+import "testing"
+
+func TestBuildProjectColumns(t *testing.T) {
+	items := []Item{{
+		ID: "1", Title: "Alpha", Kind: KindProject,
+		Raw: map[string]any{
+			"taskCount": 3, "taskCountTotal": 5,
+			"documentsCount": 2, "participantCount": 4,
+		},
+	}}
+	cols := BuildColumns(SubjectProjects, items)
+	want := []string{"_sel", "id", "title", "tasks", "documents", "users"}
+	if len(cols) != len(want) {
+		t.Fatalf("got %d columns, want %d", len(cols), len(want))
+	}
+	for i, key := range want {
+		if cols[i].Key != key {
+			t.Fatalf("col[%d]=%q want %q", i, cols[i].Key, key)
+		}
+	}
+	for _, c := range cols {
+		if c.Key == "status" || c.Key == "subtitle" {
+			t.Fatalf("unexpected column %q", c.Key)
+		}
+	}
+}
+
+func TestFormatProjectTasksOpenClosed(t *testing.T) {
+	raw := map[string]any{"taskCount": 3, "taskCountTotal": 8}
+	if got := formatProjectTasks(raw); got != "3/5" {
+		t.Fatalf("got %q want 3/5", got)
+	}
+}
+
+func TestCellTextProjectDocumentsUsers(t *testing.T) {
+	it := Item{Raw: map[string]any{"documentsCount": 7, "participantCount": 2}}
+	if got := CellText(it, "documents"); got != "7" {
+		t.Fatalf("documents: %q", got)
+	}
+	if got := CellText(it, "users"); got != "2" {
+		t.Fatalf("users: %q", got)
+	}
+}
+
+func TestBuildColumnsIncludesSelectionAndCoreFields(t *testing.T) {
+	items := []Item{
+		{ID: "1", Title: "Alpha", Kind: KindTask, Raw: map[string]any{"status": "Open"}},
+	}
+	cols := BuildColumns(SubjectTasks, items)
+	if cols[0].Key != "_sel" {
+		t.Fatalf("first column should be selection, got %q", cols[0].Key)
+	}
+}