- linkingrecord_header_check: accept "y"/"Y" for fullLoad (case-insensitive)
and add type-check before comparison to avoid misleading error on non-string values
- exterior_interior_pairing_check: introduce _get_active_prefixes() which computes
the intersection of shared prefixes that appear in BOTH exterior and interior records;
prefixes like bs-, dr-, en- that exist only in exterior features no longer poison
signatures and cause systematic false-positive failures on real packs;
when one side is entirely absent the fallback uses all shared prefixes so a
missing-interior-partner is still correctly detected
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
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