Add a public numbering module and route fragmenting, validation,
and scaffold preparation through the canonical numbering entry.
Rewrite the repository entry docs around the fixed numbering
contract, add MkDocs landing pages, and document the mirror
mapping used for medicinal-chemistry comparisons.
Also refresh the validation analysis reports to explain the
canonical-versus-mirrored numbering relationship.
Keep key validation outputs and analysis tables tracked directly,
package analysis plot PNGs into a small tar.gz backup, and add
analysis scripts plus tests so the stored results remain
reproducible without flooding git with large image trees.
