fix(nemotron_3.5_super): pin a vllm-router build with prefix affinity fixes

[sdevare-nv]

What does this PR do?

Repins the vllm-router build used by the Super 3.5 eval container, from the head of
vllm-project/router#216 to the head
of #238.

#216 fixes the decode-node hot spot (issue #197), but shipping it alone is worse than
not shipping it for prefill-heavy benchmarks like SWE-bench Pro.

#216 makes the worker load counters honest, and that switches on a second latent bug:
cache_aware decides whether to use prefix affinity from the fleet-wide load
spread, so one hot worker discards affinity for every request — including requests
whose own worker is idle. Under P/D disaggregation that gate is open almost
permanently, because prefill worker load counts queued requests as well as running
ones. Routing degenerates to shortest-queue, already-cached prompts get recomputed,
prefill saturates, and decode starves behind it.

#238 carries #216 unchanged plus a fix that applies the same load check per request,
against the worker the request actually wants, rather than against the fleet maximum.

Still fetched from vllm-project/router by bare SHA, exactly as the #216 pin already
was — a PR head is a ref in the upstream repo even when the branch lives on a
contributor's fork.

Testing

Validated on SWE-bench Pro (4 prefill / 6 decode) against two baselines on the same
checkpoint and vLLM config: the pre-#216 router, and #216 alone. With this pin the
prefill prefix-cache hit rate and end-to-end throughput return to pre-#216 behaviour
while keeping #216's decode hot-spot fix.