AI Stability & Pipeline Improvements

Added established signal and created_at to the contradiction pipeline, preparing for the ONNX contradiction classifier.

• Added _is_established() function for stable boolean classification

• Fetched created_at in ingestion traits, concepts, and reconcile sampling paths

• Removed regex-based social filter pre-router to ensure all messages flow through LLM triage

• Fixed misclassification of questions by guarding feedback matching against interrogative words

• Implemented embedding cache with 1h TTL using MemoryStore

• Reduced folder watcher scan interval from 300s to 60s for responsiveness