TS 5.7+ ArrayBuffer drift: cast where ArrayBufferLike leaked

TypeScript 5.7 split ArrayBuffer / SharedArrayBuffer at the type level
(ArrayBuffer now exposes resizable/transfer/detached etc; SharedArrayBuffer
doesn't), and parametrized the typed-array constructors so plain
Uint8Array became Uint8Array<ArrayBufferLike>.

The renderer never uses SharedArrayBuffer, so this is type-level only —
narrowing back to ArrayBuffer at the boundaries:

- BinaryReader.readBytes() / .toArrayBuffer() return the underlying
  DataView buffer; cast to ArrayBuffer.
- BinaryWriter.getBuffer() same shape.
- WsSessionCrypto.randomNonce() now returns Uint8Array<ArrayBuffer>
  (it's always backed by a plain ArrayBuffer); aesGcmEncrypt/Decrypt
  nonce parameter retyped accordingly so SubtleCrypto.encrypt accepts
  it as BufferSource.
- ArrayBufferToBase64 now accepts Uint8Array | ArrayBufferLike directly
  (pako/inflate hands back Uint8Array<ArrayBuffer> which the old
  ArrayBuffer-only signature rejected).

packages/utils/src/BinaryWriter.ts

@@ -89,7 +89,7 @@ export class BinaryWriter implements IBinaryWriter
 
     public getBuffer(): ArrayBuffer
     {
-        return this._buffer.buffer;
+        return this._buffer.buffer as ArrayBuffer;
     }
 
     public get position(): number