fix(gh-body-audit): report the $$ delimiter in the math scan

[ultimatile]

Summary

gh-body-conventions § Math rules out display math written between $$ delimiters, but the math scan in gh-body-audit reported no $$, so a body that kept such a block passed the audit. The scan now reports every line holding $$, and step 2 of gh-body-audit says how to judge each one.

Closes #243

Changes

• skills/gh-body-audit/body-math-scan.sh reports every line holding $$, as a fourth class beside Unicode math glyphs, \operatorname, and inline math neutralized by an enclosing code span. Its exit codes are unchanged: 0 clean, 1 hits, 2 usage or environment error.
• Step 2 of skills/gh-body-audit/SKILL.md judges each $$ on a reported line: one that inspection shows GitHub does not render as a math delimiter is ⊘ N/A, and any other is ⚠. An unresolved ⚠ blocks the step that called the audit, so a $$ that cannot be classified blocks it.
• Step 2 states that the $$ between two directly adjacent backtick-delimited inline-math spans is not a math delimiter: GitHub renders the two spans as inline math.
• skills/gh-body-audit/test-body-math-scan.sh covers the new class with four hit cases, two clean cases, an assertion on the printed lines, and a differential showing that the scan regex without the $$ alternative reports a $$ block clean. The test keeps three frozen regexes, the scan regex cut off after its first, second, and third class; each is built from the previous one, and one helper runs any of them.
• metadata.version in .claude-plugin/marketplace.json is 2026.10.4.

Impact

Step 2 of gh-body-audit is the scan's only caller. A body that mentions $$ in a code span now exits the scan with 1 and takes a ⊘ N/A line where it used to pass silently. A bare $$ in prose takes ⚠ unless inspection shows it renders as plain text; putting it in a code span clears the hit either way.

Verification

• bash skills/gh-body-audit/test-body-math-scan.sh printed ok for all 27 checks.
• skills/gh-body-audit/body-math-scan.sh on a body holding a $$ block exited 0 before the change and 1 after it.
• gh api -X POST /markdown in gfm mode, run on seven one-construct bodies, returned:

Body	Result
$$ on its own line above and below \{a\}	one <math-renderer> block whose content is {a}, the backslashes gone
$$x+y$$ inside a sentence	one <math-renderer>
echo $$ in a fenced sh block	code
kill $$ in a code span	code
two adjacent backtick-delimited inline-math spans	two inline <math-renderer> elements
a sentence holding one bare $$	plain text
a sentence holding two bare $$, each followed by a space	plain text

[Copilot]

Copilot review overview

🟢 Approval recommended

The scanner, audit guidance, regression coverage, and version bump consistently implement issue #243.

Review effort: Balanced
Findings: None

What changed in this PR

Adds $$ detection to the GitHub body math audit, closing #243.

Changes:

• Extends the scanner and audit guidance for $$.
• Adds regression and output tests.
• Bumps the plugin version to 2026.10.4.

File	Description
.claude-plugin/​marketplace.json	Bumps the CalVer patch version.
skills/​gh-body-audit/​SKILL.md	Documents classification of $$ hits.
skills/​gh-body-audit/​body-math-scan.sh	Adds the fourth scan class.
skills/​gh-body-audit/​test-body-math-scan.sh	Tests detection, output, and regression behavior.

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