minesweeper: narrow send(), and tell the ws mirror about the provider

two failures another session found in a shared checkout, both mine.

send() took a plain Uint8Array, whose default buffer type is
ArrayBufferLike and may be a SharedArrayBuffer — WebSocket.send takes
only BufferSource. narrowed to Uint8Array<ArrayBuffer>, which every
caller already builds and which the terminal relay already does.

registry.test.ts keeps REAL_WS as a hand-written mirror of server.tsx's
handlers map, and its own comment says that drift is what it catches. it
caught mine: the route and the registry entry landed, the mirror did not.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/workspaces/officerdev/src/apps/Minesweeper/rfb.ts

@@ -66,7 +66,10 @@ export class RfbClient {
     }
   }
 
-  private send(bytes: Uint8Array): void {
+  // Uint8Array<ArrayBuffer>, not plain Uint8Array: the default is Uint8Array<ArrayBufferLike>, whose
+  // buffer may be a SharedArrayBuffer, and WebSocket.send takes only BufferSource. Every caller here
+  // builds its own array, so narrowing costs nothing. The terminal relay narrows the same way.
+  private send(bytes: Uint8Array<ArrayBuffer>): void {
     if (this.socket.readyState === WebSocket.OPEN) this.socket.send(bytes);
   }