Extract shared cell dimming logic into DiffableTableViewCell base class

DiffableSubtitleTableViewCell and DiffableButtonTableViewCell now inherit
from DiffableTableViewCell instead of UITableViewCell directly, removing
duplicated image dimming, prepareForReuse and tintColorDidChange code.
Changed reuseIdentifier from static to class var to support overrides.
Extracted magic numbers into named constants.

Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

Update README: clarify core idea

Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

Fixed tv target.

Fixed tv target.

Fixed actionable for collection.

Added more to table diffable delegate.

Added get indexPath from datasource. Added editable flag to text fiel…

…d cells.

Updated email and assets,

Fixed collection bug with reoder section.

Fixed warnings.