Does @microsoft/signalr-protocol-msgpack support BigInt type in JavaScript?

### Is there an existing issue for this?

- [x] I have searched the existing issues

### Is your feature request related to a problem? Please describe the problem.

Does @microsoft/signalr-protocol-msgpack support BigInt type?

### Describe the solution you'd like

support BigInt type in JavaScript

### Additional context

_No response_

Start by locating the @microsoft/signalr-protocol-msgpack JavaScript package and its existing serialization tests. Investigate how JavaScript numeric values are encoded and decoded, then determine the expected BigInt behavior and compatibility requirements. Done means the package supports the requested BigInt type with tests covering the agreed behavior.

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