fix(email): add <hr> to HTML body detection (Codex P2 follow-up)

[dizhaky]

Summary

Follow-up to PR #37 Codex P2 review — the one remaining unaddressed structural gap in _is_html_body().

What changed

_HTML_TAGS in gateway/platforms/email.py (line 241) lacked hr, a common void element used in HTML digest emails. Outgoing emails whose only or first recognizable markup was <hr> or <hr/> were misclassified as plain text, sending the horizontal rule as a literal <hr> string inside a text/plain part.

One-character change: added hr| to the alternation.

Why safe

<hr> is a void element with no closing tag and takes no text content, so:

• No false-positive risk: the regex requires > or /> directly after hr, so prose comparisons like x<hr do not match.
• <style>/<script> stripping (lines 172–179) and all other _strip_html passes are unaffected.
• The _HTML_CLOSE_TAGS list (used for closing-tag detection) does not need hr since </hr> is not valid HTML.

Codex P2 status after this PR

All 15 Codex P2 findings from PR #37 are now addressed:

Finding	Status
Preserve literal HTML snippets in plain replies	Handled: _text_to_html() escapes < > & for non-HTML bodies
Recognize common standalone HTML tags (img, pre)	Fixed in commit 69871ee
Recognize <hr> standalone tag	Fixed by this PR
Preserve whitespace in generated HTML alternatives	Fixed: pre-wrap; word-wrap: break-word
Strip HTML for plain alternative	Fixed: _strip_html() on HTML bodies
Avoid treating compact comparisons as anchor tags	Fixed: anchor requires href/name attribute
Avoid matching p, code, div comparisons as HTML	Fixed: regex requires > or /> or attr=
Preserve link targets in plain fallbacks	Fixed: label (url) format
Keep block boundaries in plain fallbacks	Fixed: </p>, </li>, </tr> → newlines
Separate table cells in plain fallbacks	Fixed: </td><td> → tab
Remove style and script blocks from plain fallbacks	Fixed: lines 172–179
Keep image references in plain fallbacks	Fixed: [image: alt (url)] format
Allow generated HTML alternatives to wrap long lines	Fixed: white-space: pre-wrap

🤖 Generated with Claude Code

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Generated by Claude Code

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Note

Low Risk
Single-tag addition to an existing heuristic regex with no auth, data, or API surface changes.

Overview
Adds hr to the _HTML_TAGS alternation used by _HTML_BODY_RE / _is_html_body() in gateway/platforms/email.py.

Outgoing bodies whose only recognizable markup was a void <hr> or <hr/> were treated as plain text, so _attach_body() escaped them and recipients saw a literal <hr> string instead of a horizontal rule. With hr in the detector, those digests are classified as HTML and the HTML part is sent as-is.

No change to _HTML_CLOSE_TAGS (void element). Existing regex rules still require a real tag terminator, so prose like x<hr should not match.

^{Reviewed by Cursor Bugbot for commit 01c8bd2. Configure here.}

[github-actions]

🔎 Lint report: fix/email-hr-tag-detection vs origin/main

ruff

Total: 0 on HEAD, 0 on base (➖ 0)

🆕 New issues: none

✅ Fixed issues: none

Unchanged: 0 pre-existing issues carried over.

ty (type checker)

Total: 8649 on HEAD, 8649 on base (➖ 0)

🆕 New issues: none

✅ Fixed issues: none

Unchanged: 4570 pre-existing issues carried over.

Diagnostics are surfaced as warnings — this check never fails the build.

[chatgpt-codex-connector]

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[dizhaky]

Closing: the branch had unsigned commits (CI cursor-agent + my empty re-trigger commit). Reopened with signed commit at #40.