[codex] Configure freebuff agents by model #550

Job	Run time
build-and-smoke-freebuff-windows	2m 49s
build-freebuff	1m 26s
e2e-version	55s
e2e-help-command	1m 6s
e2e-ads-behavior	1m 6s
e2e-startup	54s
e2e-agent-startup	1m 6s
e2e-slash-commands	1m 3s
e2e-terminal-command	58s
e2e-code-edit	57s
	12m 20s

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