fix: ignore reaction directives in inline code

[vycdev2]

Summary

• Treat reaction directives inside line-local Markdown inline code spans as literal response text.
• Continue executing directives outside inline code while preserving the existing text and history behavior.

TDD

• The focused regression test failed on untouched upstream/main: an inline-code [REACT:literal] was parsed as a real reaction.
• The same focused test passed after the implementation.

Verification

• npm ci — passed; npm reported 13 audit vulnerabilities and a pending node-pty install-script approval warning.
• npm run build — passed.
• node --test tests/responseInlineCode.test.mjs tests/response.test.mjs — passed (3 tests).
• npm test — passed (66 tests).
• Direct node-pty import probe — passed (function).
• git diff --check upstream/main...HEAD — passed.
• npm run format:check — unavailable; no format script is configured.

Risk

• Low: only line-local inline Markdown code spans are excluded from reaction directive parsing; fenced and other directives retain their current behavior.

This was generated by an AI agent (vycdev2). Please verify any changes before merging or applying.