Automatic standalone structural SubDomainer

[Mining-Geologist]

Summary

• add AutomaticStructuralDomainBuilder3, independent of decoded Leapfrog labels
• generate an aspect-ratio-aware structural centroid grid
• merge only neighbouring centroid regions using deterministic SPD-matrix consistency
• enforce recovered minimum/maximum point-fraction controls
• reuse the exact LabeledStructuralDomainBuilder3 post-cluster rules
• add deterministic, arbitrary-parameter and permutation-stability tests
• add examples/standalone_automatic_lva.ipynb for arbitrary CSV/OBJ datasets

Validation boundary

This implements the recovered 6000-centroid, adjacency-constrained architecture without benchmark hardcodes. The final hidden Leapfrog tie-breaking and overlap blend equation are not serialized, so universal exact parity must be established by the regression suite rather than asserted from the implementation alone.