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/convert.go

@@ -0,0 +1,10 @@
+package preview
+
+import (
+	md "github.com/JohannesKaufmann/html-to-markdown/v2"
+)
+
+// HTMLToMarkdown converts Document Server HTML output to markdown for TUI preview.
+func HTMLToMarkdown(html string) (string, error) {
+	return md.ConvertString(html)
+}