[codex] fix DeepSeek image attachments #6407

Job	Run time
build-and-check	3m 6s
test-integration-common	40s
test-integration-sdk	1m 19s
test-integration-cli	42s
test-integration-packages/agent-runtime	44s
test-integration-packages/internal	1m 13s
test-packages/internal	50s
test-packages/agent-runtime	46s
test-packages/billing	50s
test-integration-web	52s
test-.agents	42s
test-integration-packages/billing	1m 7s
test-common	46s
test-cli	1m 2s
test-sdk	52s
test-web	2m 25s
	17m 56s

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