Address PR feedback for OpenCode integration

ui/src/lib/model-utils.ts

@@ -0,0 +1,16 @@
+export function extractProviderId(modelId: string): string | null {
+  const trimmed = modelId.trim();
+  if (!trimmed.includes("/")) return null;
+  const provider = trimmed.slice(0, trimmed.indexOf("/")).trim();
+  return provider || null;
+}
+
+export function extractProviderIdWithFallback(modelId: string, fallback = "other"): string {
+  return extractProviderId(modelId) ?? fallback;
+}
+
+export function extractModelName(modelId: string): string {
+  const trimmed = modelId.trim();
+  if (!trimmed.includes("/")) return trimmed;
+  return trimmed.slice(trimmed.indexOf("/") + 1);
+}