Fix macOS reactor close test timing

[treeform]

The reactor close test can fail on macOS when the client's disconnect packet arrives after the server's first nonblocking tick. Poll for up to 100 ticks with a 1 ms pause, keep the server's clock fixed so connection timeout cannot satisfy the assertion, and verify the disconnected connection ID.

Reproduced the original failure locally with Nim 2.2.6 on macOS. This fixes the Netty package failure reported in Nim's macOS packages job.

Validation on macOS:

• nim check tests/test_hardening.nim passed.
• 500 consecutive hardening suite runs passed.
• Main and time-series suites passed.
• A negative control that suppresses the disconnect packet failed at the expected dead-connection assertion.