fix: Round 17 audit — critical/high bug fixes (5 bugs, cross-checked)

fix: Round 14 — 28 Tier 1 + Tier 2 bugs fixed across 17 source files

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

fix: add word-level fuzzy SQL matching for country name variants

fix: SQL fuzzy matching fallback for country names with alternate forms

fix: strip trailing semicolons from LLM-generated SQL and add SQL-route fallback

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: 6-agent debug audit — 8 bugs fixed across codebase

fix: harden route parsing, column dedup, and column name access

fix: 7 bugs from multi-agent debug review of SQL layer

fix: 4 bugs found during comprehensive code review

feat: add LLM-powered column descriptions with codebook detection

fix: include sample values in SQL schema summary for better query generation

fix: prevent NameError when QU disabled and fix connection leak

feat: add SQL result formatting and schema summary builder

feat: add SQL retriever — validated read-only query execution