compaction-artifact-preservation-universally-scores-2.2-out-of-5

All compression methods (summarize, extract, chunk, hybrid) score 2.2–2.5/5.0 on artifact preservation — the weakest dimension universally across tested approaches. The failure mode is embedding file paths, function names, and error codes inside prose summaries, which get compressed away on subsequent passes. Fix: maintain a separate verbatim artifact trail index (not embedded in prose) in PreCompact hooks, and validate survival via a dedicated Artifact probe in PostCompact.