Unify macrolactone detection, numbering, fragmentation, and
splicing under the installable macro_lactone_toolkit package.
- replace legacy src.* modules with the new package layout
- add analyze/number/fragment CLI entrypoints and pixi tasks
- migrate tests, README, and scripts to the new package API
- Add src/splicing/ module with scaffold_prep, fragment_prep, and engine
- Add tylosin_splicer.py entry script
- Add unit tests for splicing components
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
