fix: publish session.error event for invalid model selection (#8451)

packages/opencode/src/session/prompt.ts

@@ -321,7 +321,18 @@ export namespace SessionPrompt {
           history: msgs,
         })
 
-      const model = await Provider.getModel(lastUser.model.providerID, lastUser.model.modelID)
+      const model = await Provider.getModel(lastUser.model.providerID, lastUser.model.modelID).catch((e) => {
+        if (Provider.ModelNotFoundError.isInstance(e)) {
+          const hint = e.data.suggestions?.length ? ` Did you mean: ${e.data.suggestions.join(", ")}?` : ""
+          Bus.publish(Session.Event.Error, {
+            sessionID,
+            error: new NamedError.Unknown({
+              message: `Model not found: ${e.data.providerID}/${e.data.modelID}.${hint}`,
+            }).toObject(),
+          })
+        }
+        throw e
+      })
       const task = tasks.pop()
 
       // pending subtask