feat: HTML file cards should render inline in chat like the Markdown preview #247

Hello,

HTML files displayed in chat only appear as a "click to open" card, while Markdown files render directly inline, so viewing a generated report requires an extra tap and a full-screen context switch.

Current behavior

• .md file cards render their content directly in the chat message.
• .html file cards only open a separate full-screen preview view (iframe + toolbar) when tapped.

Desired behavior

• Render the HTML document inline in the chat card: height-capped (e.g. 300–400 px), internally scrollable, and rendered in a sandboxed iframe pointing at the existing /api/workspace/files/serve/<path> endpoint.
• The existing full-screen preview view stays available as a secondary action (e.g. an "expand" affordance on the inline card).
• Include a cache-busting parameter in the inline iframe URL so the preview always reflects the current file.

Acceptance criteria:

• .html file cards render the document inline (height-capped, scrollable) without an extra tap.
• Tapping the inline card (or an explicit expand button) opens the existing full-screen preview.
• The inline iframe uses a cache-busting URL parameter.
• Behavior is verified for a self-contained HTML file.

Thanks for considering this. It would make HTML artifacts (reports, dashboards, generated documents) as glanceable as Markdown, especially on mobile.

Best regards,
Joshua Krimmer