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/ui/detail_test.go

@@ -0,0 +1,49 @@
+package ui_test
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/eslider/go-onlyoffice/cmd/office/model"
+	"github.com/eslider/go-onlyoffice/cmd/office/ui"
+)
+
+func TestEntityFormLoadAndView(t *testing.T) {
+	form := ui.NewEntityFormForTest()
+	form.SetSize(40, 16)
+	form.Load(model.KindTask, "42", model.FormFields{
+		PrimaryLabel: "Title", SecondaryLabel: "Description",
+		Primary: "Fix bug", Secondary: "Details here",
+	})
+	view := form.View()
+	if !strings.Contains(view, "Fix bug") {
+		t.Fatal("view missing title")
+	}
+}
+
+func TestDetailPaneFormAndActions(t *testing.T) {
+	d := ui.NewDetailPaneForTest()
+	d.SetSize(50, 20)
+	d.SetFocused(true)
+	d.LoadForm(model.Item{ID: "1", Kind: model.KindTask, Title: "T"}, model.FormFields{
+		PrimaryLabel: "Title", SecondaryLabel: "Description",
+		Primary: "Hello", Secondary: "World",
+	})
+	view := d.View()
+	if !strings.Contains(view, "Save") {
+		t.Fatal("expected Save action button")
+	}
+	if !strings.Contains(view, "Hello") {
+		t.Fatal("expected form content")
+	}
+}
+
+func TestDetailPaneDocumentMode(t *testing.T) {
+	d := ui.NewDetailPaneForTest()
+	d.SetSize(50, 20)
+	d.LoadDocument(model.Item{ID: "9", Kind: model.KindFile, Title: "a.txt"}, "# Doc\n\nbody", 40)
+	view := d.View()
+	if !strings.Contains(view, "Download") {
+		t.Fatal("expected Download action")
+	}
+}