Route deepseek-v4-flash to Fireworks when DeepSeek API is unhealthy #6760

Job	Run time
build-and-check	2m 52s
test-integration-packages/internal	1m 6s
test-integration-packages/billing	1m 4s
test-integration-web	46s
test-integration-common	40s
test-integration-cli	54s
test-integration-sdk	1m 27s
test-integration-packages/agent-runtime	50s
test-cli	52s
test-packages/internal	56s
test-packages/billing	43s
test-packages/agent-runtime	49s
test-.agents	45s
test-common	40s
test-web	59s
test-sdk	48s
	16m 11s

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