Compare pyright to mypy, and document type checking approach

[jpmckinney]

pyright seems to be faster, more comprehensive, and less buggy.

We might be able to eliminate some annotations and guards that we added (e.g. to credere-backend) to get mypy to pass.

We might need to keep mypy where plugins are relevant (if used with Django, apparently).

If switching, rename workflows to types.yml

Not sure if there is an advantage to using mypy in combination with mypyc (e.g. if there are shared assumptions of behavior) re: #113

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In any case, we should document how to set up whichever tool, e.g.:

[tool.mypy]
strict = true
warn_unreachable = true
exclude = "(build|docs|tests)/"

  - repo: https://github.com/pre-commit/mirrors-mypy
    rev: v1.12.0
    hooks:
      - id: mypy
        exclude: "(docs|tests)/"
        additional_dependencies:
          - types-orjson
          - types-pika