Quantco/pixi-pack

AI Summary: The task requires integrating the concurrency configuration from the `rattler_config` crate into the `pixi-pack` project. This involves using the concurrency settings defined in `rattler_config` (specifically, the `Concurrency` struct and its related functions) to control the parallel execution within `pixi-pack`'s operations, likely during the package downloading or unpacking phases.

AI Summary: Modify the `pixi-pack` Rust code to allow packing Python wheels from local paths, instead of only accepting URLs or paths within a local PyPI server. This involves adjusting the `download_pypi_package` function to handle local file paths similarly to how it handles cached packages, ensuring compatibility checks are still performed.