ci(release): swap retired macos-13 runner for macos-15-intel #232

Job	Run time
governance / Well-Known (RFC 9116 + RSR)	4s
governance / Security policy checks	4s
governance / Workflow security linter	6s
governance / Code quality + docs	15s
governance / Guix primary / Nix fallback policy	6s
governance / Language / package anti-pattern policy	6s
	41s

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