feat(mypy): add num_workers for parallel type checking

[wasimat404]

Closes #5826.

mypy 2.0 added experimental parallel type checking via the num_workers config option (the --num-workers / -n CLI flag), but the schema's additionalProperties: false rejects it, so editors like Even Better TOML flag num_workers as an unexpected property. This adds it to the global options block in partial-mypy.json. It's a global-only option, so it's intentionally not added to the per-module overrides section. The entry matches the existing verbosity style (plain description, integer type, default 0) and I extended the existing mypy-01.toml positive test with num_workers = 4 rather than adding a new fixture.

Worth flagging for maintainers: the schema looks broadly stale relative to mypy 2.0/2.1, since it was last generated before 2.0 shipped in May. native_parser was exposed in the same 2.0 release (python/mypy#21387) and is also missing here. I kept this PR scoped to the reported issue, but a fuller regeneration pass against the current docs would be worthwhile as a follow-up if someone wants to pick it up.

Validation: node cli.js check --schema-name=pyproject.json passes, and prettier is clean on both files.

[github-actions]

Thanks for the PR!

This section of the codebase is owned by @madskristensen and @hyperupcall - if they write a comment saying "LGTM" then it will be merged.