docs: restore ADR-020 + ADR-021 + coordination ledger (lost in #344 squash) #344

Job	Run time
governance / Language / package anti-pattern policy	43s
governance / Workflow security linter	35s
governance / Well-Known (RFC 9116 + RSR)	34s
governance / Guix primary / Nix fallback policy	34s
governance / Code quality + docs	29s
governance / Security policy checks	35s
	3m 30s

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