fix(autoep+muon): auto-fill HF config fields and restore batched NS
Two fixes addressing masahiro's review feedback on PR #7938:
1. Auto-fill AutoEPConfig from HF model config (auto_ep_config.py,
auto_ep.py): add fill_autoep_config_from_hf() which maps HF field
names to AutoEP internal names on AutoEP.__init__:
- n_group -> num_expert_groups
- topk_group -> num_limited_groups
- routed_scaling_factor -> route_scale
User-supplied values always take precedence. Without this, Moonlight
(DeepSeek-V3) training used route_scale=1.0 instead of 2.446,
producing systematically wrong MoE output magnitudes.
2. Restore batched Newton-Schulz in muon_update (original_muon.py):
replace the per-expert Python loop with a single batched call to
zeropower_via_newtonschulz5, which already supports ndim>=2 inputs.
This restores GPU parallelism across all E experts per step.
Signed-off-by: Ma, Guokai <guokai.ma@gmail.com>