fix(editor): render paired inline HTML tags

[murongg]

Summary

• render balanced source-authored inline HTML pairs such as <sup>...</sup> as real inline elements in the visual editor
• preserve the underlying HTML boundary nodes so nested Markdown remains editable and serialization/reload stay unchanged
• preserve soft line breaks before inline HTML when the visual editor serializes back into the source pane
• reuse the existing raw HTML sanitizer for URLs and attributes, while leaving malformed and block-level boundaries on their current path

Why

Milkdown represents inline raw HTML as separate opening and closing atoms. Rendering each atom independently made opening tags disappear and closing tags fall back to visible source.

The Markdown stringifier also normalizes a soft break immediately before an HTML node into a space. In split mode, the deferred visual update then wrote that normalized line back to the source pane. This PR marks single-line HTML tokens only while stringifying so their original line breaks survive without changing the ProseMirror document.

Validation

• pnpm test passed: 2,412 tests
• pnpm build passed, including desktop vendor chunk verification
• pnpm --filter @markra/app typecheck:test passed
• focused inline HTML, raw HTML, and line-break integration tests passed: 7 tests

Risk

• paired rendering is limited to a strict inline-tag allowlist
• rendered attributes pass through the existing sanitizer; unsafe URLs and event attributes remain removed
• the serializer marker is limited to non-empty, single-line HTML source; multiline block HTML keeps the existing serialization path

Note

  is the Markdown serializer preserving a trailing space and reproduces without HTML. This PR does not strip it because doing so would make source round-trips lossy.

Closes #543

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Project	Deployment	Actions	Updated (UTC)
markra-web	Ready	Preview, Comment	Jul 17, 2026 5:59am