P1: implement real Zig FFI matching the Idris2 ABI (#30) #53

Job	Run time
governance / Licence consistency	7s
governance / Security policy checks	5s
governance / Well-Known (RFC 9116 + RSR)	6s
governance / Trusted-base reduction policy	8s
governance / Check Workflow Staleness	5s
governance / Code quality + docs	10s
governance / Guix primary / Nix fallback policy	5s
governance / Language / package anti-pattern policy	11s
governance / Workflow security linter	7s
governance / Validate Hypatia Baseline	-1s
	1m 3s

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