ci: SessionStart hook to auto-provision Agda toolchain on the web #402

Job	Run time
governance / Code quality + docs	14s
governance / Language / package anti-pattern policy	8s
governance / Licence consistency	10s
governance / Security policy checks	7s
governance / Guix primary / Nix fallback policy	4s
governance / Well-Known (RFC 9116 + RSR)	3s
governance / Workflow security linter	5s
governance / Trusted-base reduction policy	9s
governance / Validate Hypatia baseline	9s
	1m 9s

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