docs: clarify test file structure convention in CLAUDE.md (#2006) #524

Job	Run time
checks / readme-snippets	13s
checks / pre-commit	40s
checks / test (3.10, locked, windows-latest)	2m 15s
checks / test (3.10, locked, ubuntu-latest)	50s
checks / test (3.10, lowest-direct, ubuntu-latest)	57s
checks / test (3.11, lowest-direct, ubuntu-latest)	55s
checks / test (3.11, locked, ubuntu-latest)	44s
checks / test (3.14, locked, windows-latest)	3m 29s
checks / test (3.12, lowest-direct, windows-latest)	3m 43s
checks / test (3.12, locked, windows-latest)	3m 20s
checks / test (3.12, lowest-direct, ubuntu-latest)	59s
checks / test (3.12, locked, ubuntu-latest)	55s
checks / test (3.10, lowest-direct, windows-latest)	2m 31s
checks / test (3.13, locked, windows-latest)	2m 21s
checks / test (3.13, lowest-direct, ubuntu-latest)	55s
checks / test (3.11, lowest-direct, windows-latest)	2m 47s
checks / test (3.13, locked, ubuntu-latest)	48s
checks / test (3.13, lowest-direct, windows-latest)	2m 35s
checks / test (3.11, locked, windows-latest)	2m 39s
checks / test (3.14, lowest-direct, windows-latest)	2m 17s
checks / test (3.14, lowest-direct, ubuntu-latest)	1m 23s
checks / test (3.14, locked, ubuntu-latest)	2m 21s
all-green	4s
	39m 41s

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