c4bbb14e52
- _build_anchor_index(): regex-harvests PR/issue numbers, SHAs, branches, file paths, error strings, handles, URLs from the compacted region into a bounded indexed summary section. LLM-free, so needle identifiers cannot be paraphrased away (the GUI-lineage failure class: 10/15 verbatim-or-nothing golds). Doubles as session_search query-anchor map. - evals/compaction/test_region_scoping.py: sentinel tripwire proving the summarizer input carries ONLY the compacted region (head/tail sentinels never reach the serialized turns body) in both legacy and lean modes.