refactor(entities/Font): relocate FontSampler from DisplayFont, invert typography

DisplayFont was not a feature (FSD+ A-6): the whole slice was one
presentational component that renders a Font styled by typography, with no
model/domain/action. To get typography it reached sideways into a sibling
feature (`$features/AdjustTypography/model`) — a feature->feature edge
(C-1), the symptom of the mislayering, not the disease.

Fix by inversion, mirroring the existing `status` prop pattern:

- move FontSampler into entities/Font/ui (it now uses only entity siblings
  + $shared/ui)
- it accepts a `typography` prop typed to a minimal contract defined in the
  component; the AdjustTypography store satisfies it structurally, so the
  entity has no dependency on the feature
- SampleList (owns both) injects its typographySettingsStore as the prop
- delete the DisplayFont slice; export FontSampler from the Font barrel;
  relocate the story (now passes a mock typography)

Resolves A-6, A-7, and the FontSampler half of C-1. Verified: 0 type
errors, 0 lint (boundary rule satisfied), 905 unit + 213 component tests,
production build OK.

src/entities/Font/index.ts

@@ -19,6 +19,7 @@ export type { FontRowSizeResolverOptions } from './lib';
 
 export {
     FontApplicator,
+    FontSampler,
     FontVirtualList,
 } from './ui';