Merge BlockstreamResearch/Simplicity#335: Detach the jet codec #6

Job	Run time
build (haskell, ubuntu-latest, nixos-25.05)	24m 31s
build (c, macos-latest, nixos-25.05)	4m 6s
build (c, ubuntu-latest, nixpkgs-unstable)	1m 4s
build (haskell, ubuntu-latest, nixpkgs-unstable)	25m 3s
build (c, ubuntu-latest, nixos-25.05)	1m 2s
build (c, macos-latest, nixpkgs-unstable)	3m 3s
build (haskell, macos-latest, nixpkgs-unstable)	37m 38s
build (haskell, macos-latest, nixos-25.05)	36m 20s
codespell	13s
	2h 13m 0s

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