chore: src/ README audit gate + 5 package READMEs (#126, #152) (#71) #67

Job	Run time
Lint & Format	10s
Architecture (import-linter)	13s
Pre-commit	1m 7s
Unit tests	21s
Type Check	19s
Coverage	21s
File length	6s
Branch-protection contexts sync	11s
Frontend Build	14s
Commit-type sync	11s
src/ README audit	6s
Action pinning audit	6s
Frontend Quality	20s
Version bump check	-1s
Tests required	-1s
	3m 43s

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