fix: resolve Windows CI failures and markdown lint (#667)

- Replace node -e with temp file execution in validator tests to avoid
  Windows shebang parsing failures (node -e cannot handle scripts that
  originally contained #!/usr/bin/env node shebangs)
- Remove duplicate blank line in skills/rust-patterns/SKILL.md (MD012)

skills/rust-patterns/SKILL.md

@@ -43,7 +43,6 @@ fn process_bad(data: &Vec<u8>) -> usize {
 }
 ```
 
-
 ### Use `Cow` for Flexible Ownership
 
 ```rust