Update dialog renders raw changelog Markdown and does not truncate

The "Update OpenPencil" dialog for 0.15.1 shows the changelog section verbatim: ### Added / ### Changed / ### Fixed headings appear as literal text, bullets are unformatted, and the dialog grows to the full height of the release notes with no scroll or limit.

Expected:

• Render the changelog section as Markdown (headings, lists, inline code).
• Cap the dialog height and scroll the notes, or show a short summary with a "View full release notes" link.
• Consider following the platform-standard updater dialog layout (version, short notes, Update / Later).