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/preview/render_test.go

@@ -0,0 +1,31 @@
+package preview_test
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/eslider/go-onlyoffice/cmd/office/preview"
+)
+
+func TestRenderMarkdown(t *testing.T) {
+	out, err := preview.RenderMarkdown("# Hello\n\nWorld", 40)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if out == "" {
+		t.Fatal("empty render output")
+	}
+	if !strings.Contains(strings.ToLower(out), "hello") {
+		t.Fatalf("expected rendered heading: %q", out)
+	}
+}
+
+func TestRenderMarkdownEmpty(t *testing.T) {
+	out, err := preview.RenderMarkdown("", 40)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if strings.TrimSpace(out) != "" {
+		t.Fatalf("expected empty, got %q", out)
+	}
+}