Update Muon blog with measured convergence and memory data
Replace placeholder claims with actual experiment results:
- Add lr sweep results for both AdamW and Muon optimizers
- Report measured GPU memory: AdamW 34.5 GiB vs Muon 31.4 GiB (9% savings)
- Remove old convergence chart (adamw_vs_muon_3b.png)
- Fix inaccurate claims (Muon 19% better, Adam OOM on 2xA100)
- Add hybrid optimizer explanation and separate lr config docs
Signed-off-by: Ma, Guokai <guokai.ma@gmail.com>
