Move left pane entirely to React

ts/state/reducer.ts

@@ -0,0 +1,25 @@
+import { combineReducers } from 'redux';
+
+import { reducer as search, SearchStateType } from './ducks/search';
+import {
+  ConversationsStateType,
+  reducer as conversations,
+} from './ducks/conversations';
+import { reducer as user, UserStateType } from './ducks/user';
+
+export type StateType = {
+  search: SearchStateType;
+  conversations: ConversationsStateType;
+  user: UserStateType;
+};
+
+export const reducers = {
+  search,
+  conversations,
+  user,
+};
+
+// Making this work would require that our reducer signature supported AnyAction, not
+//   our restricted actions
+// @ts-ignore
+export const reducer = combineReducers(reducers);