docs: modernize development guidelines and rename to AGENTS.md (#2413) #1845

Job	Run time
checks / readme-snippets	17s
checks / pre-commit	32s
checks / test (3.11, locked, windows-latest)	2m 43s
checks / test (3.11, locked, ubuntu-latest)	53s
checks / test (3.10, locked, windows-latest)	2m 35s
checks / test (3.11, lowest-direct, ubuntu-latest)	57s
checks / test (3.12, lowest-direct, ubuntu-latest)	1m 1s
checks / test (3.10, lowest-direct, windows-latest)	3m 1s
checks / test (3.11, lowest-direct, windows-latest)	2m 37s
checks / test (3.10, lowest-direct, ubuntu-latest)	1m 1s
checks / test (3.12, lowest-direct, windows-latest)	4m 8s
checks / test (3.14, locked, windows-latest)	3m 35s
checks / test (3.13, lowest-direct, ubuntu-latest)	52s
checks / test (3.12, locked, ubuntu-latest)	53s
checks / test (3.13, lowest-direct, windows-latest)	2m 39s
checks / test (3.14, locked, ubuntu-latest)	2m 24s
checks / test (3.10, locked, ubuntu-latest)	52s
checks / test (3.14, lowest-direct, windows-latest)	2m 46s
checks / test (3.13, locked, windows-latest)	2m 32s
checks / test (3.13, locked, ubuntu-latest)	50s
checks / test (3.12, locked, windows-latest)	2m 41s
checks / test (3.14, lowest-direct, ubuntu-latest)	1m 20s
all-green	4s
	41m 13s

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