Enable OpenCode Zen for any opencode/-prefixed model #582

Job	Run time
build-freebuff	1m 8s
build-and-smoke-freebuff-windows	2m 30s
e2e-version	1m 10s
e2e-slash-commands	1m 5s
e2e-terminal-command	59s
e2e-help-command	1m 6s
e2e-startup	1m 8s
e2e-code-edit	1m 10s
e2e-agent-startup	2m 33s
e2e-ads-behavior	1m 18s
	14m 7s

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