Return error when running uvx with a .py script (#11623)
If we see `uvx script.py`, we exit early, giving a hint to use `uv run
script.py` if the script exists. If it does not exist, we suggest
running `uv run` with a normalized package name.
This PR includes a snapshot test for each of these scenarios.
An alternative approach would be to wait until we encounter an error,
and then add the hint. But if there happens to be a malicious package
called `script-py`, this would be run unintentionally (a point raised by
@zanieb).
Closes #10784
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Co-authored-by: Zanie Blue <contact@zanie.dev>
