[codex] Use baseline Bun target for Windows builds #6641

Job	Run time
build-and-check	2m 57s
test-integration-packages/billing	1m 13s
test-integration-packages/internal	1m 8s
test-integration-web	39s
test-integration-cli	40s
test-integration-packages/agent-runtime	42s
test-integration-sdk	1m 18s
test-cli	54s
test-integration-common	39s
test-packages/billing	45s
test-packages/agent-runtime	45s
test-common	45s
test-sdk	40s
test-.agents	40s
test-web	57s
test-packages/internal	52s
	15m 34s

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