Local updates

fix: pre-release audit round 12 — 33 bugs fixed across all tiers

feat: brief KB overview for system prompt + original query cross-check

feat: LLM-generated welcome summary for knowledge base contents

fix: Round 8 audit — 15 bugs fixed across 10 files (1 CRITICAL, 7 HIGH, 3 MEDIUM, 4 LOW)

fix: 10 bugs (4 HIGH + 6 MEDIUM) from comprehensive codebase audit

fix: harden source display, subdirectory paths, and chunk ID uniqueness

docs: update README with KB self-awareness section and fix missing connection note

feat: add KB meta overview for meta-question answering and LLM awareness