fix: prevent single-tilde strikethrough false positives

src/Tokenizer.ts

@@ -866,6 +866,13 @@ export class _Tokenizer<ParserOutput = string, RendererOutput = string> {
 
         // Create del token - only single ~ or double ~~ supported
         const text = raw.slice(lLength, -lLength);
+
+        // For single ~, skip if closing ~ is followed by an alphanumeric character.
+        // Prevents e.g. `~125 GeV, while the top quark is **~173 GeV**` from matching as strikethrough,
+        // since the closing ~ fails GFM right-flanking delimiter rules.
+        // See https://github.github.com/gfm/#emphasis-and-strong-emphasis
+        if (lLength === 1 && raw.length < src.length && /[0-9a-zA-Z]/.test(src[raw.length])) continue;
+
         return {
           type: 'del',
           raw,

test/specs/new/del_flanking.html

@@ -3,3 +3,4 @@
 <p>Between (~1.34) and (~5.4)</p>
 <p>~ test~</p>
 <p>~test ~</p>
+<p>The mass of the Higgs boson is ~125 GeV, while the top quark is <strong>~173 GeV</strong></p>

test/specs/new/del_flanking.md

@@ -7,3 +7,5 @@ Between (~1.34) and (~5.4)
 ~ test~
 
 ~test ~
+
+The mass of the Higgs boson is ~125 GeV, while the top quark is **~173 GeV**