fix(nestjs): treat WsException as expected error

[7inspire]

This PR updates NestJS expected-error detection to avoid reporting WsException control-flow errors to Sentry.

Why

Issue #19631 notes that WsException should be treated similarly to HttpException and RpcException (control-flow exceptions thrown by user code), and should not be captured as errors.

What changed

• Updated isExpectedError in packages/nestjs/src/helpers.ts:
  • Keep existing getError + initMessage detection (covers current RpcException/WsException shapes).
  • Add a WsException fallback for variants that expose getError but not initMessage, detected via constructor.name === 'WsException'.
• Added test coverage in packages/nestjs/test/helpers.test.ts for a WsException-like object without initMessage.

Risk

Low. The change is scoped to NestJS control-flow exception classification and does not alter event pipeline behavior outside this filter.

Validation

• Added unit test for the new WsException fallback case.
• Note: Full test execution was not run in this environment because yarn is unavailable.

[nicohrubec]

Why do you think we need this? Did you find any old version specifically that would require this fallback? Else we will likely close this, because it seems to be already covered by our current logic since WsException and RpcException expose basically the same interface.