### Summary
This PR hides `<dyad-command type="refresh"></dyad-command>` tags from
generated text outputs. These elements are not intended for end users
and clutter the response text.

### Changes
- Filter out `<dyad-command>` tags from generated text.
- Ensure no regressions in rendering or formatting of user-visible
output.

    
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## Summary by cubic
Hide dyad-command tags from chat output so internal commands never
appear in user-visible text. Updates DyadMarkdownParser to detect and
drop these tags during preprocessing, parsing, and rendering.

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