- Added new `replace` hashline edit operation for substring-style fuzzy text replacement without line references, with optional `all` flag for replace-all behavior.
- Added `noopEdits` array to `applyHashlineEdits` return value to report edits that produced no changes, including edit index, location, and current content for diagnostics.
- Added validation to detect and reject hashline edits using wrong-format fields (`old_text`/`new_text` from replace mode, `diff` from patch mode) with helpful error messages.
- Renamed hashline edit operation keys from `single`/`range`/`insertAfter` to `set_line`/`replace_lines`/`insert_after` for clearer semantics.
- Enhanced error messages for wrong-format hashline edits to guide users toward correct operation syntax.