feat(ui): change intermediates handling

- Update the canvas graph generation to flag its uploaded init and mask images as `intermediate`.
- During canvas setup, hit the update route to associate the uploaded images with the session id.
- Organize the socketio and RTK listener middlware better. Needed to facilitate the updated canvas logic.
- Add a new action `sessionReadyToInvoke`. The `sessionInvoked` action is *only* ever run in response to this event. This lets us do whatever complicated setup (eg canvas) and explicitly invoking. Previously, invoking was tied to the socket subscribe events.
- Some minor tidying.

invokeai/frontend/web/src/features/system/store/actions.ts

@@ -0,0 +1,3 @@
+import { createAction } from '@reduxjs/toolkit';
+
+export const sessionReadyToInvoke = createAction('system/sessionReadyToInvoke');

invokeai/frontend/web/src/features/system/store/sessionSlice.ts

@@ -0,0 +1,62 @@
+// TODO: split system slice inot this
+
+// import type { PayloadAction } from '@reduxjs/toolkit';
+// import { createSlice } from '@reduxjs/toolkit';
+// import { socketSubscribed, socketUnsubscribed } from 'services/events/actions';
+
+// export type SessionState = {
+//   /**
+//    * The current socket session id
+//    */
+//   sessionId: string;
+//   /**
+//    * Whether the current session is a canvas session. Needed to manage the staging area.
+//    */
+//   isCanvasSession: boolean;
+//   /**
+//    * When a session is canceled, its ID is stored here until a new session is created.
+//    */
+//   canceledSessionId: string;
+// };
+
+// export const initialSessionState: SessionState = {
+//   sessionId: '',
+//   isCanvasSession: false,
+//   canceledSessionId: '',
+// };
+
+// export const sessionSlice = createSlice({
+//   name: 'session',
+//   initialState: initialSessionState,
+//   reducers: {
+//     sessionIdChanged: (state, action: PayloadAction<string>) => {
+//       state.sessionId = action.payload;
+//     },
+//     isCanvasSessionChanged: (state, action: PayloadAction<boolean>) => {
+//       state.isCanvasSession = action.payload;
+//     },
+//   },
+//   extraReducers: (builder) => {
+//     /**
+//      * Socket Subscribed
+//      */
+//     builder.addCase(socketSubscribed, (state, action) => {
+//       state.sessionId = action.payload.sessionId;
+//       state.canceledSessionId = '';
+//     });
+
+//     /**
+//      * Socket Unsubscribed
+//      */
+//     builder.addCase(socketUnsubscribed, (state) => {
+//       state.sessionId = '';
+//     });
+//   },
+// });
+
+// export const { sessionIdChanged, isCanvasSessionChanged } =
+//   sessionSlice.actions;
+
+// export default sessionSlice.reducer;
+
+export default {};