The escape-brackets checkbox label loses its underscore to mnemonic parsing #547

QueryStoreGridControl.axaml:180: CheckBox Content="Treat [ ] _ as literals". AccessText takes the character after the first underscore as an access key and strips the underscore from display, so the label renders as "Treat [ ] as literals" — losing the underscore that is half of what the checkbox is about (a LIKE wildcard). Pre-existing on Avalonia 11 and unchanged by 12 (found during the upgrade's access-key review). Fix: escape it as __ or reword the label.