Fix button cell showing black text on initial display

Set tintColor explicitly in cell provider so the text color
is correct from the start, not only after tintColorDidChange.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Simplify image dimming to pure tintColorDidChange swap

The previous approach tried to detect original vs desaturated images
by comparing references in updateImageDimming(), which broke on undim:
the method read the desaturated image back from contentConfiguration
and overwrote the stored original with it.

Now tintColorDidChange simply saves the original on dim and restores
it on undim — no separate method, no flags, no heuristics. Cell
providers no longer need to call updateImageDimming() manually.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Remove saveOriginal parameter from updateImageDimming

The parameter leaked internal caching logic into the public call sites.
Now the method auto-detects a new original image via identity check
(content.image !== originalImage), so callers no longer need to know
about the caching mechanism.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

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) <noreply@anthropic.com>

Update README: clarify core idea

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

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.