docs: add AI-assisted contribution policy to CONTRIBUTING.md (#2887) #2760

Job	Run time
checks / readme-snippets	12s
checks / pre-commit	42s
checks / test (3.10, lowest-direct, windows-latest)	1m 25s
checks / test (3.11, locked, windows-latest)	1m 44s
checks / test (3.12, locked, ubuntu-latest)	57s
checks / test (3.10, locked, windows-latest)	1m 26s
checks / test (3.11, locked, ubuntu-latest)	56s
checks / test (3.12, locked, windows-latest)	1m 33s
checks / test (3.11, lowest-direct, windows-latest)	1m 45s
checks / test (3.12, lowest-direct, ubuntu-latest)	1m 5s
checks / test (3.10, locked, ubuntu-latest)	1m 0s
checks / test (3.12, lowest-direct, windows-latest)	1m 25s
checks / test (3.10, lowest-direct, ubuntu-latest)	59s
checks / test (3.14, locked, ubuntu-latest)	1m 29s
checks / test (3.13, locked, ubuntu-latest)	55s
checks / test (3.11, lowest-direct, ubuntu-latest)	1m 3s
checks / test (3.14, locked, windows-latest)	2m 13s
checks / test (3.13, locked, windows-latest)	1m 27s
checks / test (3.13, lowest-direct, ubuntu-latest)	59s
checks / test (3.14, lowest-direct, windows-latest)	1m 25s
checks / test (3.14, lowest-direct, ubuntu-latest)	52s
checks / test (3.13, lowest-direct, windows-latest)	1m 31s
all-green	3s
	27m 6s

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