Feature: --assert-time to assert response latency

[korya]

Problem

The tool already measures and prints request duration:

[+] PASSED 1.469625ms

…but there is no way to assert on it. --max-time is a hard timeout that produces a transport error, not a latency assertion with a clean diagnostic.

Proposed

--assert-time duration   Assert the response arrived within the given duration

Failure output would then read:

- time: expected <= 500ms, got 1.203s

Why it matters

Latency SLOs are a routine thing to check in monitoring and post-deploy validation, and the measurement is already in hand — this is mostly plumbing.