Add DeepSeek V4 provider #6335

Job	Run time
build-and-check	3m 7s
test-integration-packages/billing	1m 5s
test-integration-packages/internal	1m 9s
test-integration-cli	53s
test-integration-web	42s
test-integration-sdk	1m 20s
test-integration-packages/agent-runtime	46s
test-packages/internal	48s
test-sdk	49s
test-common	44s
test-web	2m 30s
test-packages/billing	39s
test-.agents	46s
test-cli	50s
test-packages/agent-runtime	54s
test-integration-common	47s
	17m 49s

Provide feedback