- Replaced atom sed parsing and operations with replace-based edit schema (`find`, `with`, `all`) and `replace_file`.
- Removed bracketed/range locator handling and delimiter-based block APIs, including `splice_block` workflows.
- Restricted Atom locator parsing to one anchor or `$` with line > 0 and enforced line-only targets.
- Updated atom docs and tests to cover the new replace semantics, anchor-only edits, and literal newline limits.