Fix: Escape literal % in LIKE pattern in B1 metadata diagnostic

psycopg2 performs %-substitution when params are passed to execute(),
so 'M%' in the LIKE clause was being interpreted as a positional
placeholder, raising IndexError when there's only one real %s (LIMIT).
Escape as 'M%%' so it's preserved as a literal percent.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Python-Version/scripts/diagnose_b1_master_metadata.py

@@ -55,7 +55,7 @@ def main():
         cursor.execute("""
             SELECT tracking_id, original_filename, full_metadata
             FROM master_assets
-            WHERE tracking_id LIKE 'M%'
+            WHERE tracking_id LIKE 'M%%'
               AND local_campaign_id IS NULL
               AND status = 'active'
             ORDER BY created_at DESC