fix: resolve Swift 6.0 type inference issues in RealtimeTests

This commit fixes two Swift 6.0 compiler errors that were causing CI
failures on Xcode 16.4:

1. In setUp(), explicitly unwrap the `client` implicitly unwrapped
   optional when captured in the wsTransport closure
2. In testBroadcastWithHTTP(), explicitly unwrap the `sut` implicitly
   unwrapped optional when captured in the mock response closure

These changes are needed because Swift 6.0 is stricter about type
inference with implicitly unwrapped optionals in closure capture lists.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

Author: grdsdev

Tests/RealtimeTests/RealtimeTests.swift

@@ -49,7 +49,7 @@ final class RealtimeTests: XCTestCase {
           "custom.access.token"
         }
       ),
-      wsTransport: { [client] _, _ in client },
+      wsTransport: { [client] _, _ in client! },
       http: http
     )
   }
@@ -581,7 +581,7 @@ final class RealtimeTests: XCTestCase {
       HTTPResponse(
         data: "{}".data(using: .utf8)!,
         response: HTTPURLResponse(
-          url: sut.broadcastURL,
+          url: sut!.broadcastURL,
           statusCode: 200,
           httpVersion: nil,
           headerFields: nil