npm style script support

[allenc97]

Summary

Currently, uv supports entrypoint scripts but strictly requires package installation, which is problematic for standard applications with no packaging intentions. It would be great to support certain features of npm's scripts, e.g defining commands that are pre-configured with certain flags, as a new subcommand.

Example

In similar fashion to npm:
"run_with_debug": "uv run --directory src flask --app hello run --debug" -> uv execute run_with_debug
Assuming paths are properly configured, this would also allow the user to execute a command such as the one above from any subdirectory under the project's root.

[cthoyt]

you should check out similar issue with long discussion: #5903