uv run should not require an existing virtual environment

[zanieb]

Currently uv run fails if a virtual environment is not present

❯ uv run --with anyio -- python -c "print('hi')"
warning: `uv run` is experimental and may change without warning.
error: Failed to locate a virtualenv or Conda environment (checked: `VIRTUAL_ENV`, `CONDA_PREFIX`, and `.venv`). Run `uv venv` to create a virtualenv.

We should not require a virtual environment to exist to run commands.

You can currently bypass this with --isolated

❯ uv --isolated run --with anyio -- python -c "print('hi')"
warning: `uv run` is experimental and may change without warning.
Resolved 3 packages in 195ms
Downloaded 3 packages in 78ms
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 + anyio==4.3.0
 + idna==3.7
 + sniffio==1.3.1
hi

[charliermarsh]

Are you sure this is true on main? It works fine for me.

[charliermarsh]

I'm thinking of: #3499

[zanieb]

Ah I was running the latest release, presuming you fixed this then.