- Added hashline edit mode for line-addressed edits using hash-verified line references with xxHash64 integrity verification.
- Replaced `edit.patchMode` boolean setting with `edit.mode` enum supporting 'replace', 'patch', and 'hashline' modes.
- Added `readHashLines` configuration setting to include line hashes in read output for hashline edit mode.
- Implemented `computeLineHash`, `formatHashLines`, `parseLineRef`, `validateLineRef`, and `applyHashlineEdits` utility functions for hashline operations.
- Updated read tool to support optional `hashes` parameter and prioritize hash lines over line numbers when both are requested.
- Changed `getEditModelVariants()` return type from `Record<string, 'patch' | 'replace'>` to `Record<string, EditMode | null>` and removed hardcoded model-specific defaults.