Refreshes stale PR #320 with the same minimal fix and focused coverage.

PythonShell.runString() currently builds its temp file path with the imported tmpdir function reference instead of calling tmpdir(). That can produce an invalid path before PythonShell.run() is reached.

This change uses path.join(tmpdir(), ...) and adds a regression test that intercepts PythonShell.run() to verify:

• the generated script path is in the OS temp directory
• the generated file contains the provided code
• the original run options are passed through unchanged

Verification:

• npm test -- --grep "runString"
• npm test
• npx prettier --check index.ts test/test-python-shell.ts
• git diff --check
• review-fix-loop: no actionable regressions found