Remove `type: ignore` mypy comments

Remove type: ignore comments.

Current counts for each ignored mypy error code:

• exit-return: 1
• func-returns-value: 1
• has-type: 1
• list-item: 1
• return: 1
• truthy-bool: 1
• used-before-def: 1
• method-assign: 2
• return-value: 2
• truthy-iterable: 2
• comparison-overlap: 3
• dict-item: 5
• type-arg: 5
• redundant-expr: 6
• operator: 7
• call-overload: 8
• import-not-found: 8
• index: 8
• no-redef: 9
• name-defined: 10
• union-attr: 14
• override: 15
• unreachable: 16
• arg-type: 18
• assignment: 25
• possibly-undefined: 37
• var-annotated: 42
• valid-type: 79
• misc: 89
• call-arg: 90
• attr-defined: 247
• import-untyped: 483
• no-untyped-def: 927

Start by locating the Python files containing the listed type: ignore comments and group them by mypy error code. Review each ignored error and determine the required typing or code change before removing the comment. Done means the listed ignore counts reach zero and mypy no longer reports those errors.