Add bool guard before the int branch in _cell_to_str so True/False cells are preserved as "True"/"False" instead of "1"/"0". Add two regression tests covering the fix and missing-sheet error. Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
Add bool guard before the int branch in _cell_to_str so True/False cells are preserved as "True"/"False" instead of "1"/"0". Add two regression tests covering the fix and missing-sheet error. Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>