test+docs: API 키 안내 경로 단위 테스트 + ops 문서 #11

Job	Run time
realdata-plan	14s
cross-os-smoke (windows-latest)	2m 25s
fixture-integration	8m 47s
test-full (3.12)	13m 22s
cross-os-smoke (macos-latest)	1m 28s
cross-os-smoke (ubuntu-latest)	57s
test-full (3.13)	13m 7s
realdata-suite	0s
	40m 20s

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