chore: stricter mypy #4482

Job	Run time
Linters (mypy, flake8, etc.)	1m 31s
Get qemu emulated architectures	9s
Test on ubuntu-latest (3.13)	41m 24s
Test cibuildwheel building pyodide wheels	5m 21s
Test on windows-latest (3.13)	44m 20s
Test on macos-13 (3.13)	24m 47s
Test on macos-14 (3.13)	12m 42s
Test on ubuntu-latest (3.8)	38m 48s
Test Linux aarch64 using qemu	26m 36s
Test Linux armv7l using qemu	9m 0s
Test Linux ppc64le using qemu	17m 52s
Test Linux s390x using qemu	19m 18s
	4h 1m 48s

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