[Bugfix] Fix nemotron accuracy drop introduced by #41184

[bnellnm]

Purpose

The routed_scaling_factor was getting applied twice in the Nemotron model. We needed to check apply_routed_scaling_factor_to_output before passing the scaling factor onto the RoutedExperts.

Test Plan

pytest -sv tests/evals/gsm8k/test_gsm8k_correctness.py::test_gsm8k_correctness[Nemotron-3-Super-120B-A12B-NVFP4] --config-list-file=configs/models-blackwell-ep.txt

Test Result

Test passed.

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[GirasoleY]

Additional validation on another model that hits the same generic DeepSeek/FusedMoE routed-scale path:

• Kimi-K2.5-NVFP4, GSM8K, NQ=100, dcp=1: current main before this fix was 25% accuracy; with this routed_scaling_factor fix it recovers to 92%.
• This is the dense generic FusedMoE / ModelOpt NVFP4 path, not the sparse-attention path, so it validates the same double-application of routed_scaling_factor beyond Nemotron.

This matches the root cause described in this PR: when apply_routed_scale_to_output=True, RoutedExperts must receive the router-side scale (1.0) while MoERunner owns the output-side scale.