Author ML knowledge skills (pkbllm)

Goal

Add a new ML knowledge skill under knowledge/ML/ that matches this repo’s conventions and stays high-signal.

Curated ML taxonomy (fixed)

Put new ML skills under exactly one of these categories:

• model-architecture/
• training/ (post-training)
• distributed/
• serving/
• paper/
• kernel/ (to fill)
• agents/ (to fill)

If it doesn’t fit, don’t add it. Extend taxonomy only with explicit repo-level intent.