[codex] Improve binary spawn errors #789

Job	Run time
build-and-smoke-freebuff-windows	2m 39s
build-freebuff	1m 15s
e2e-terminal-command	59s
e2e-help-command	1m 22s
e2e-version	1m 8s
e2e-agent-startup	2m 28s
e2e-startup	1m 22s
e2e-code-edit	51s
e2e-slash-commands	53s
e2e-ads-behavior	1m 10s
	14m 7s

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