refactor(chat): route browser chat through one runtime (P3 Slice-Zero Task 5) (#1172)

Co-authored-by: shaggy <[email protected]>

apps/web/src/spa/chat/test-support/fake-chat-socket.ts

@@ -14,6 +14,10 @@ export interface EmittedEvent<K extends ClientEvent = ClientEvent> {
 /** The subset of a Socket.IO `ChatSocket` that `useChatConnection` drives. */
 export interface FakeChatSocket {
   connected: boolean;
+  /** Mirrors socket.io-client's `Socket.id`: the connection identity the server
+   * echoes in a `chat:send-capability` payload. The generation-bound send
+   * protocol accepts an advertisement only when `payload.connectionId === id`. */
+  id: string;
   connect(): FakeChatSocket;
   on<K extends ServerEvent>(event: K, handler: ServerHandler<K>): FakeChatSocket;
   off<K extends ServerEvent>(event: K, handler: ServerHandler<K>): FakeChatSocket;
@@ -51,8 +55,10 @@ export function createFakeChatSocket(): {
   /** Simulates socket.io-client's automatic reconnect of the *same*
    * instance after a transient disconnect: marks the socket connected again
    * and fires any handler(s) registered via `socket.on('connect', ...)`,
-   * without clearing or replacing any listeners. */
-  simulateReconnect(): void;
+   * without clearing or replacing any listeners. A real reconnect is assigned
+   * a fresh `Socket.id`; pass `nextId` to model that new connection identity
+   * (defaults to the current id so existing callers are unaffected). */
+  simulateReconnect(nextId?: string): void;
 } {
   const listeners = new Map<ServerEvent, Set<(payload: never) => void>>();
   const emitted: EmittedEvent[] = [];
@@ -63,6 +69,7 @@ export function createFakeChatSocket(): {
   // type-checked against ServerToClientEvents/ClientToServerEvents.
   const socket = {
     connected: false,
+    id: 'socket-a',
     connect: vi.fn(function connect(this: void) {
       socket.connected = true;
       return socket;
@@ -105,8 +112,9 @@ export function createFakeChatSocket(): {
     }
   }
 
-  function simulateReconnect(): void {
+  function simulateReconnect(nextId: string = socket.id): void {
     socket.connected = true;
+    socket.id = nextId;
     const lifecycleKey = 'connect' satisfies LifecycleEvent as unknown as ServerEvent;
     for (const handler of listeners.get(lifecycleKey) ?? []) {
       (handler as () => void)();