Add DeepSeek V4 provider #6347

Job	Run time
build-and-check	3m 7s
test-integration-packages/billing	1m 14s
test-integration-packages/internal	1m 14s
test-integration-cli	47s
test-integration-web	48s
test-integration-sdk	2m 9s
test-integration-common	42s
test-integration-packages/agent-runtime	46s
test-packages/billing	44s
test-packages/internal	54s
test-common	44s
test-packages/agent-runtime	49s
test-web	1m 3s
test-cli	50s
test-.agents	42s
test-sdk	41s
	17m 14s

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