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/layout_test.go

@@ -0,0 +1,69 @@
+package ui
+
+import (
+	"testing"
+
+	"github.com/eslider/go-onlyoffice/cmd/office/model"
+)
+
+func TestLayoutWidthsAllVisibleUsesFullWidth(t *testing.T) {
+	vis := PaneVisibility{Menu: true, List: true, Detail: true}
+	pw := LayoutWidths(120, vis)
+	sum := pw.Menu + pw.List + pw.Detail
+	if sum != 120 {
+		t.Fatalf("sum=%d want 120", sum)
+	}
+}
+
+func TestLayoutWidthsSinglePane(t *testing.T) {
+	pw := LayoutWidths(100, PaneVisibility{Menu: false, List: true, Detail: false})
+	if pw.List != 100 {
+		t.Fatalf("list=%d want 100", pw.List)
+	}
+	if pw.Menu != 0 || pw.Detail != 0 {
+		t.Fatalf("unexpected widths: %+v", pw)
+	}
+}
+
+func TestLayoutWidthsTwoPanes(t *testing.T) {
+	pw := LayoutWidths(80, PaneVisibility{Menu: true, List: false, Detail: true})
+	if pw.Menu+pw.Detail != 80 {
+		t.Fatalf("sum=%d want 80", pw.Menu+pw.Detail)
+	}
+}
+
+func TestNextVisibleFocusSkipsHidden(t *testing.T) {
+	vis := PaneVisibility{Menu: false, List: true, Detail: true}
+	if got := NextVisibleFocus(model.FocusList, vis); got != model.FocusPreview {
+		t.Fatalf("got %v", got)
+	}
+	if got := NextVisibleFocus(model.FocusPreview, vis); got != model.FocusList {
+		t.Fatalf("got %v", got)
+	}
+}
+
+func TestPrevVisibleFocusSkipsHidden(t *testing.T) {
+	vis := PaneVisibility{Menu: true, List: false, Detail: true}
+	if got := PrevVisibleFocus(model.FocusPreview, vis); got != model.FocusMenu {
+		t.Fatalf("got %v", got)
+	}
+}
+
+func TestLayoutWidthsLegacyHelper(t *testing.T) {
+	menu, list, preview := LayoutWidthsLegacy(120)
+	if menu+list+preview != 120 {
+		t.Fatalf("widths exceed total")
+	}
+}
+
+func TestKeyActionTogglePanes(t *testing.T) {
+	if got := KeyAction("alt+1", model.FocusList); got != ActionToggleMenuPane {
+		t.Fatalf("got %v", got)
+	}
+	if got := KeyAction("alt+2", model.FocusMenu); got != ActionToggleListPane {
+		t.Fatalf("got %v", got)
+	}
+	if got := KeyAction("alt+3", model.FocusList); got != ActionToggleDetailPane {
+		t.Fatalf("got %v", got)
+	}
+}