feat(office): add Workspace TUI with shared bootstrap and test suite

Introduce the office Bubble Tea browser (module tree, multi-select lists,
markdown preview) alongside oo, with cmd/internal/bootstrap for shared auth,
unit tests across preview/model/ui/fetch, CI build for both binaries, and
GoReleaser archives for office.

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

cmd/office/ui/app_test.go

@@ -0,0 +1,42 @@
+package ui_test
+
+import (
+	"testing"
+
+	"github.com/eslider/go-onlyoffice/cmd/office/model"
+	"github.com/eslider/go-onlyoffice/cmd/office/ui"
+)
+
+func TestKeyActionMenuDown(t *testing.T) {
+	if got := ui.KeyAction("j", model.FocusMenu); got != ui.ActionMoveDown {
+		t.Fatalf("got %v", got)
+	}
+}
+
+func TestKeyActionListToggleSelect(t *testing.T) {
+	if got := ui.KeyAction(" ", model.FocusList); got != ui.ActionToggleSelect {
+		t.Fatalf("got %v", got)
+	}
+}
+
+func TestKeyActionPreviewNoOp(t *testing.T) {
+	if got := ui.KeyAction(" ", model.FocusPreview); got != ui.ActionNone {
+		t.Fatalf("got %v", got)
+	}
+}
+
+func TestKeyActionTabNextPane(t *testing.T) {
+	if got := ui.KeyAction("tab", model.FocusList); got != ui.ActionNextPane {
+		t.Fatalf("got %v", got)
+	}
+}
+
+func TestLayoutWidths(t *testing.T) {
+	menu, list, preview := ui.LayoutWidths(120)
+	if menu+list+preview > 120 {
+		t.Fatalf("widths exceed total: %d+%d+%d", menu, list, preview)
+	}
+	if menu < 20 || list < 30 || preview < 30 {
+		t.Fatalf("widths too narrow: %d %d %d", menu, list, preview)
+	}
+}