Add pyproject.toml auto-formatting.

[dpranke]

This change primarily adds a dev dependency on the pyproject-fmt package to auto-format the pyproject.toml file, and adds the logic to do so to ./run format. The implementation is kinda convoluted because the package has an inconvenient interface and returns a 1 when it successfully formats a file that needed changes, rather than returning 0.

This change also reformats json5/tool.py and updates the uv.lock file to pick up newer packages. I'm of mixed feelings about uv.lock updating existing packages whenever a new dependency is added (rather than only updating expackages when explicitly asked to do so), so I can see changing the logic for how we're managing packages in the future either back to explicitly pinning versions by default, or to do something else.

[dpranke]

@ulgens - thoughts?

[ulgens]

@dpranke I prefer to use pyproject-fmt as a git hook, with the following config:

[tool.pyproject-fmt]
indent = 4
keep_full_version = true
max_supported_python = ...

• It's isolated from the functional dependencies. I like the "wrap linters with git hook and use the hooks in CI" approach.
• Using indent 4 mostly because of personal taste, but I also think it fits with Python's standard tab width.

[dpranke]

Yeah, git hooks would probably work too. I'll switch to your settings, as I have no strong opinions and 4 spaces appears to match what uv init does.