Bump mypy to 2.0.0 and enable parallel checking

[adamtheturtle]

Summary

• Bump mypy[faster-cache] from 1.20.2 to 2.0.0 in dev dependencies.
• Pass --num-workers=4 to the mypy and mypy-docs pre-commit hooks to use mypy 2.0's new parallel type-checking.

Test plan

• Pre-push hooks pass (mypy + mypy-docs).

🤖 Generated with Claude Code

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Note

Low Risk
Low risk: only updates dev tooling and pre-push hooks, but mypy 2.0 may introduce new/changed type-checking errors that could block contributors’ pre-push workflow.

Overview
Upgrades dev dependency mypy[faster-cache] from 1.20.2 to 2.0.0.

Updates the mypy and mypy-docs pre-push hooks to pass --num-workers=4, enabling mypy’s parallel type-checking for faster runs.

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