Add DeepSeek V4 provider #6336

Job	Run time
build-and-check	2m 44s
test-integration-packages/internal	1m 2s
test-integration-packages/billing	1m 2s
test-integration-packages/agent-runtime	44s
test-integration-cli	50s
test-integration-common	42s
test-integration-sdk	1m 18s
test-integration-web	50s
test-packages/internal	47s
test-.agents	44s
test-packages/billing	44s
test-sdk	50s
test-common	40s
test-cli	55s
test-packages/agent-runtime	45s
test-web	1m 5s
	15m 42s

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