This adds a new configuration option `searchDisabledChoices` that allows
disabled choices to appear in search results while remaining non-selectable.
Previously, disabled choices were always excluded from search results via
the Store's searchableChoices getter. This made it impossible for users to
find disabled options even when they wanted to see what options exist but
are currently unavailable.
Changes:
- Add searchDisabledChoices option to Options interface (default: false)
- Update Store.searchableChoices getter to respect the new config
- Add test coverage for the new functionality
- Maintain backward compatibility with default behavior
The selection prevention logic in _handleChoiceAction already prevents
disabled choices from being selected, so they remain non-selectable even
when found in search results.
Fixes the limitation where users couldn't search for disabled options to
see what choices exist but are currently unavailable.
