Robust Judge API parsing and schemas validation default values for 0.5B model support

Update schemas.py EmbeddingModel enum to replace EmbeddingGemma with bge-small-en

Few tweaks

RAG retreival updates

Restore Phase 5 advanced RAG changes and clean schemas.py

initial: RAG Visualizer (Phases 1-4)

local: phase 5 arena and text highlighter