docs: fix stub pages and improve docs structure #4201

Job	Run time
checks / pre-commit	44s
checks / test (3.11, lowest-direct, ubuntu-latest)	49s
checks / test (3.11, highest, ubuntu-latest)	47s
checks / test (3.12, lowest-direct, windows-latest)	3m 21s
checks / test (3.10, lowest-direct, ubuntu-latest)	45s
checks / test (3.12, lowest-direct, ubuntu-latest)	47s
checks / test (3.13, lowest-direct, windows-latest)	2m 38s
checks / test (3.11, lowest-direct, windows-latest)	2m 24s
checks / test (3.10, lowest-direct, windows-latest)	2m 29s
checks / test (3.10, highest, ubuntu-latest)	48s
checks / test (3.12, highest, ubuntu-latest)	51s
checks / test (3.13, highest, windows-latest)	2m 31s
checks / readme-snippets	15s
checks / test (3.13, lowest-direct, ubuntu-latest)	45s
checks / test (3.13, highest, ubuntu-latest)	48s
checks / test (3.11, highest, windows-latest)	2m 33s
checks / test (3.12, highest, windows-latest)	3m 30s
checks / test (3.10, highest, windows-latest)	2m 17s
all-green	3s
	29m 5s

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