[sdojjy]

Bulk INSERT doubled percent signs in bound strings, so inserting 50% through executemany stored 50%% while a single INSERT stored 50%. Remove percent escaping from data values, decode compiled SQL percent escapes once, and decode the optimized batch prefix without rewriting bound data.

Validation:

• PASS: 64 unit tests, including single/bulk values and compiled percent-containing identifiers.
• PASS: real warehouse Core INSERT/SELECT, metadata reflection, ORM mapping and streamed results on SQLAlchemy 1.4.54 and 2.1.8.
• PASS: original implementation reproduced the value mismatch; corrected implementation preserves quotes, backslashes, Unicode and percent signs.
• PASS: whitespace checks.