Add JavaScript and TypeScript aliases

[timzhong1024]

Summary

• accept javascript and typescript as aliases for the Node toolchain
• document the aliases in both READMEs and the bundled Agent Skill
• add parser coverage for canonical Node normalization

Verification

• cargo fmt --check
• cargo test --locked (20 passed)
• cargo clippy --locked --all-targets -- -D warnings
• quick_validate.py skills/run-code-snippet
• executed snippets through both aliases
• cargo package --locked --allow-dirty