fix: default cross-lingual off, concept-matrix cache, in-corpus demo prompts, UI cache styling

feat(optimizations): implement 7 low-latency non-LLM RAG adaptations and 750-query benchmark suite

feat: extend Indic RAG pipeline to all 14 Indic languages + English with FAISS indexes, centroids, and multi-language tests

fix(pipeline): critical network killswitch, FAISS self-healing startup, post-retrieval confidence calibration, and semantic answer cache