Make Reader and Writer stricter about their args. Use pathlib.Paths … #203

Job	Run time
pre-commit	18s
build_wheel_and_sdist	13s
mypy-strict	10s
test_on_all_platforms (3.10, windows-latest)	48s
test_on_all_platforms (3.9, ubuntu-24.04)	42s
test_on_all_platforms (3.10, macos-latest)	46s
test_on_all_platforms (3.11, windows-latest)	52s
test_on_all_platforms (3.10, ubuntu-24.04)	39s
test_on_all_platforms (3.15-dev, ubuntu-24.04)	40s
test_on_all_platforms (3.14, macos-latest)	47s
test_on_all_platforms (3.9, windows-latest)	1m 35s
test_on_all_platforms (3.15-dev, macos-latest)	50s
test_on_all_platforms (3.11, macos-latest)	34s
test_on_all_platforms (3.11, ubuntu-24.04)	28s
test_on_all_platforms (3.12, macos-latest)	34s
test_on_all_platforms (3.13, macos-latest)	31s
test_on_all_platforms (3.9, macos-latest)	51s
test_on_all_platforms (3.13, windows-latest)	50s
test_on_all_platforms (3.13, ubuntu-24.04)	34s
test_on_all_platforms (3.15-dev, windows-latest)	1m 45s
test_on_all_platforms (3.12, ubuntu-24.04)	35s
test_on_all_platforms (3.14, ubuntu-24.04)	25s
test_on_all_platforms (3.12, windows-latest)	1m 18s
test_on_all_platforms (3.14, windows-latest)	58s
	17m 43s

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