[codex] Add incremental chat completion traces #6681

Job	Run time
build-and-check	3m 8s
test-integration-packages/internal	1m 4s
test-integration-packages/billing	1m 12s
test-integration-packages/agent-runtime	48s
test-integration-cli	43s
test-integration-common	45s
test-integration-sdk	1m 17s
test-integration-web	48s
test-packages/agent-runtime	45s
test-packages/internal	53s
test-sdk	45s
test-cli	58s
test-web	1m 2s
test-common	42s
test-.agents	43s
test-packages/billing	44s
	16m 17s

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