[codex] Clarify string tool input errors (#599) #512

Job	Run time
build-freebuff	1m 20s
build-and-smoke-freebuff-windows	2m 14s
e2e-terminal-command	1m 3s
e2e-version	1m 25s
e2e-help-command	1m 20s
e2e-startup	1m 13s
e2e-slash-commands	58s
e2e-ads-behavior	1m 10s
e2e-code-edit	1m 5s
e2e-agent-startup	2m 21s
	14m 9s

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