Clarify `--project` flag help text to indicate project discovery
Update the help text for `--project` from "Run the command within
the given project directory" to "Discover a project in the given
directory" to better reflect its actual behavior.
The `--project` flag affects file discovery (pyproject.toml, uv.toml,
etc.) but does not change the working directory. Users should use
`--directory` for changing the working directory.
Fixes#16718
Oshadha Gunawardena
2abe56a357