- skip fused/shared/multi-anchor side systems during extraction
- add fragment library schema and fragment_library.csv export
- make scaffold prep strict for non-spliceable positions
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
