Add opencode.yml #656

Job	Run time
rust_ci (windows-latest, beta)	50s
rust_ci (ubuntu-latest, stable)	58s
rust_ci (macos-latest, stable)	49s
rust_ci (windows-latest, stable)	47s
rust_ci (macos-latest, beta)	53s
rust_ci (ubuntu-latest, beta)	43s
	5m 0s

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