Enable OpenCode Zen for minimax + kimi; add buffbench agents (#624) #6535

Job	Run time
build-and-check	2m 54s
test-integration-packages/internal	59s
test-integration-packages/billing	1m 1s
test-integration-sdk	1m 18s
test-integration-cli	51s
test-integration-common	50s
test-integration-web	43s
test-integration-packages/agent-runtime	46s
test-cli	56s
test-common	39s
test-web	1m 13s
test-.agents	38s
test-packages/billing	46s
test-sdk	44s
test-packages/internal	56s
test-packages/agent-runtime	48s
	16m 2s

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