Release 0.4.2: heredoc trailing code fix

[jeanpaulsio]

Summary

• Bump to 0.4.2
• Heredocs with trailing code (foo(<<~SQL), <<~HEREDOC.strip) now parse without errors
• Updated README known limitations to reflect the fix

What's in 0.4.2

• fix: Heredoc tokenizer uses hybrid approach — full token when no trailing code, opener-only when trailing code exists
• All 105 tests pass

Test plan

• npm run build clean
• npm test — 105 passing
• README updated
• Version bumped in package.json