[codex] Improve binary spawn errors (#724) #790

Job	Run time
build-and-smoke-freebuff-windows	2m 25s
build-freebuff	1m 14s
e2e-ads-behavior	1m 17s
e2e-version	1m 7s
e2e-slash-commands	1m 4s
e2e-agent-startup	2m 40s
e2e-code-edit	1m 6s
e2e-help-command	1m 19s
e2e-terminal-command	53s
e2e-startup	1m 6s
	14m 11s

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