Avoid shell parsing for Python helper commands

[StantonMatt]

Summary

• replace shell-string execution in checkSyntaxFile, getVersion, and getVersionSync with argument-vector execFile calls
• fix paths with spaces for explicit Python executable paths and syntax-checked file paths
• add regressions for getVersion(), getVersionSync(), and checkSyntaxFile() paths containing spaces

Fixes #181.

Why

The previous implementation built commands like ${pythonPath} --version. That breaks when the Python executable path contains spaces and also leaves these helpers dependent on shell parsing. Passing the executable and arguments separately avoids quoting issues.

Verification

• npm test -- --grep "path contains spaces|executable path contains spaces"
• npm test
• npx prettier --check index.ts test/test-python-shell.ts
• git diff --check
• review-fix-loop: clean, no introduced correctness/security/maintainability issues