- Added a `= A..B` hashline rule and adjacent-edge guidance to the tool prompt.
- Added `HashlineReplacementGroup` and `HashlineDeleteEdit` with helpers to find anchor-target lines.
- Added `findReplacementGroup()` and duplicate-boundary absorption to normalize edits with synthetic deletes and warnings.
- Added normalization flow into `applyHashlineEdits` before bucketing, and added duplicate-boundary edge-case tests.
- Updated `CHANGELOG.md` with Added and Fixed unreleased notes for hashline boundary-line behavior.