docs: restructure documentation with quickstart, concepts, and new nav #522

Job	Run time
checks / readme-snippets	14s
checks / pre-commit	37s
checks / test (3.10, lowest-direct, ubuntu-latest)	46s
checks / test (3.11, lowest-direct, ubuntu-latest)	46s
checks / test (3.10, lowest-direct, windows-latest)	2m 23s
checks / test (3.13, locked, windows-latest)	2m 51s
checks / test (3.12, locked, ubuntu-latest)	51s
checks / test (3.12, lowest-direct, windows-latest)	3m 34s
checks / test (3.14, locked, windows-latest)	3m 30s
checks / test (3.14, lowest-direct, ubuntu-latest)	1m 16s
checks / test (3.11, locked, windows-latest)	2m 20s
checks / test (3.13, lowest-direct, ubuntu-latest)	47s
checks / test (3.11, locked, ubuntu-latest)	45s
checks / test (3.12, locked, windows-latest)	3m 9s
checks / test (3.10, locked, ubuntu-latest)	45s
checks / test (3.10, locked, windows-latest)	2m 27s
checks / test (3.13, lowest-direct, windows-latest)	3m 5s
checks / test (3.11, lowest-direct, windows-latest)	2m 53s
checks / test (3.12, lowest-direct, ubuntu-latest)	48s
checks / test (3.14, lowest-direct, windows-latest)	2m 12s
checks / test (3.14, locked, ubuntu-latest)	2m 25s
checks / test (3.13, locked, ubuntu-latest)	45s
all-green	2s
	39m 11s

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