Port upstream Muya inline math scrollbar fix

[Renakoni]

Summary

• Port upstream MarkText PR #4839 into the Android Muya copy.
• Prevent KaTeX inline math ending in subscript/superscript nodes from producing a stray horizontal scrollbar.
• Scope the CSS to .mu-math > .mu-math-render so the fix only affects rendered inline math inside the editor.

Upstream Source

• Upstream PR: fix(muya): stop inline math showing a scrollbar for trailing sub/superscripts (#4837) marktext/marktext#4839
• Upstream issue: [Bug] Inline $...$ math shows a horizontal scrollbar when there is a subscript (0.20.0-beta.5) marktext/marktext#4837

Android Relevance

This is relevant to Android because the Android editor renders Muya inline math inside the WebView. The upstream bug is caused by KaTeX layout internals: .vlist-s contributes extra scroll width and .vlist-t2 uses a negative right margin that fixes visible layout but leaves scrollWidth wider than the rendered formula. Since Muya's inline math render container allows horizontal overflow, short formulas ending in subscript/superscript can show an unnecessary scrollbar.

Change Details

• Zero .katex .vlist-s width and min-width inside Muya inline math render output.
• Reset .katex .vlist-t2 right margin in the same scoped render path.
• Kept the change local to the existing Muya inline syntax stylesheet instead of introducing a separate Android override.

Verification

• pnpm build passed before commit on this branch.