Round-1 review F2. The escapeHtmlAttr (&,",<,>) and escapeHtmlText (&,<,>)
helpers in turndown.utils were untested — every existing round-trip case used
alphanumeric values, so no escape branch ran. A mention/status carrying HTML
special chars would re-emit malformed HTML that import's parseHTML can't
restore → the same data loss this PR fixes, uncaught.
Add a round-trip case to turndown.dataloss.test.ts: a mention with `&` and `"`
in both data-label and visible text. Assert (a) the exported Markdown carries
the correctly-escaped, well-formed tag (data-label="A & "B"",
text escapes &), not the raw malformed form; and (b) markdownToHtml restores
the original unescaped values (attribute `A & "B"`, text `@A & "B"`).
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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