Expand `~` to the home directory in the configuration files

[leodevian]

Summary

Path entries in the configuration file are not resolved, making it hard to write and share standard uv.toml configuration files.

On Windows, using the following uv.toml to provide user-level configuration would create directories named ~ in whatever directory uv was called from while it needed its cache.

cache-dir = "~/.cache/uv"

Resolving ~ as the home directory would enable to universal, shareable configuration files.

Furthermore, I doubt that ~ is used for anything other than referencing home directories.

Example

cache-dir = "~/.cache/uv"

This user-level or system-level uv.toml would make uv create its cache in the home directory of the user.