Add DeepSeek V4 provider (#574) #6348

Job	Run time
build-and-check	3m 9s
test-integration-packages/billing	1m 24s
test-integration-packages/internal	1m 8s
test-integration-cli	43s
test-integration-web	44s
test-integration-common	59s
test-integration-packages/agent-runtime	50s
test-common	38s
test-integration-sdk	1m 15s
test-packages/billing	51s
test-packages/internal	46s
test-packages/agent-runtime	46s
test-cli	1m 2s
test-sdk	42s
test-.agents	46s
test-web	1m 18s
	17m 1s

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