Ability to add comments in Markdown Preview Mode

Request

Please add support for leaving review comments while viewing a Markdown file in Preview Mode.

Reasoning

As AI-assisted workflows become more common, more of the important review context is showing up in Markdown files, not just code. Things like planning docs, specs, implementation notes, READMEs, and BMAD-style workflow docs are becoming a much bigger part of the review process.

Preview Mode is the best way to review that content because it shows the Markdown as it is actually intended to be read. But right now, if I want to leave a review comment, I have to switch back to the raw Markdown source. That breaks the flow and makes it harder to review and comment on symbol heavy components; such as tables, ascii diagrams, etc.

It would be really helpful to support comments directly from Preview Mode since it would make reviewing Markdown-heavy PRs much smoother and more natural.

Examples

BMad Method, where teams work through Markdown artifacts such as PRDs, architecture documents, story files, and user guides, and Superpowers, which uses Markdown specs and implementation plans as key workflow artifacts. In these kinds of frameworks, Markdown files are not just supporting docs; they are a primary medium for planning, review, and inter-agent coordination.

I am aware of this previous feature-request post, but it was made 2+ years ago and seems like it never went anywhere. I think the importance of this has changed drastically since then. - https://github.com/microsoft/vscode-pull-request-github/issues/5382

リンクされた以前の機能リクエストである issue #5382 を読み、この拡張機能で Markdown Preview Mode と review comments がどのように扱われているかを追跡することから始めてください。プレビューでの操作を定義し、レビュアーが Markdown コンテンツを選択してコメントを残し、ソースビューに切り替えることなく期待されるレビューコンテキストを維持できることを確認してください。