fixing auto-launch to bail out fast when cudaq-qpud dies

[sacpis]

• If the launched server exits before becoming reachable, waitpid(WNOHANG) breaks out of the 50s ping loop so we move to the next port immediately, instead of throwing RuntimeError: No usable ports available only after few minutes.
• Dropping static from the mt19937 so seed_offset is honoured on every construction, not just the first one.

Fixes:

 @pytest.fixture(scope="session", autouse=True)
    def startUpMockServer():
>       cudaq.set_target("remote-mqpu", auto_launch=str(num_qpus))
E       RuntimeError: No usable ports available

tmp/tests/remote/test_remote_platform.py:71: RuntimeError

https://github.com/NVIDIA/cuda-quantum/actions/runs/25393104770/job/74490650292#step:7:1282

[atgeller]

LGTM, thanks @sacpis!

[1tnguyen]

👍

[github-actions]

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Run #25403817603 · ✅ 6 · ⏩ 7 · ❌ 0 · ⛔ 0

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