Ensure workflows load the real Playwright runtime

[G-Fourteen]

Summary

• prefer the real Playwright package when it is available and fall back to the stub otherwise
• delegate the python -m playwright CLI to the official implementation when present while retaining stub fallback
• expose the Error class from the stub so tests can import it when the real package is unavailable

Testing

• pytest

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https://chatgpt.com/codex/tasks/task_b_6905fa4d1e1483299f5231e3a290f25d