[Designer] #215 Polish AI settings + frame suggestion surfaces
- frame_suggestion_dialog: hide exception detail in error path, redesign
candidate card as Card+InkWell with L2/L3 colored level badge (secondary
vs primary), remove confidence % surface.
- settings_screen: download tile gains state label + colored progress text,
rounded LinearProgressIndicator, FilledButton.tonalIcon for resume/retry.
_friendlyError() maps internal codes (network:/http /stream:/sha mismatch)
to user-readable Korean. Opt-in/out dialogs reorganized with _Bullet rows;
beta disclaimer reworded; _describe() friendlier copy.
Polish only — no behavior change. analyze 0, 71 tests pass, APK 10.3s.
Refs #215
joungmin
71e8c3dd53