T512: balanced reference coverage

All existing roots and all original attachments are unchanged. The original generate.py still reproduces the complete root selection. This revision clarifies the bounded reference-coupling rationale and attaches an additional fresh validation.
To run the extra endpoint/index checks, obtain the table document as JSON and use:
    python balanced_root_checks.py T512 table.json

All pre-existing number strings, entry metadata, order of parameters and TID are retained. The old values have mixed-source provenance: this run rechecks them, but does not claim to have originally produced them. New numbers use 100 significant digits unless exact.
Selection roles and sources are in balanced-source-research.json and the completeness note. Exploratory reference cutoffs are explicitly noncanonical.