Add activeModelSelector

Active Model details are used in multiple places. So makes sense to have a selector for it.

invokeai/frontend/src/features/system/store/systemSelectors.ts

@@ -1,6 +1,31 @@
+import { createSelector } from '@reduxjs/toolkit';
 import { RootState } from 'app/store';
 import { SystemState } from './systemSlice';
+import _ from 'lodash';
 
 export const systemSelector = (state: RootState): SystemState => state.system;
 
 export const toastQueueSelector = (state: RootState) => state.system.toastQueue;
+
+export const activeModelSelector = createSelector(
+  systemSelector,
+  (system) => {
+    const { model_list } = system;
+    const activeModel = _.reduce(
+      model_list,
+      (acc, model, key) => {
+        if (model.status === 'active') {
+          acc = key;
+        }
+        return acc;
+      },
+      ''
+    );
+    return { ...model_list[activeModel], name: activeModel };
+  },
+  {
+    memoizeOptions: {
+      resultEqualityCheck: _.isEqual,
+    },
+  }
+);