feat(design): the field family, the dropdown trigger, native controls, the no-raw-input lint rule (E28 S3c)

- ui/Input, Textarea, InnerInput + fieldClass (A4): the >= 3:1 edge, a 2px accent
  focus edge, the danger edge for invalid, md/sm/xs/heading rungs, 1rem and 44 on touch
- ui/SelectTrigger (A5): SortControl, FilterSelect, the view switcher and the date
  filter on one trigger, a pill in a toolbar, r8 in a form
- ui/NativeControls (A6): Checkbox, CheckRow, Slider, ColorInput
- every raw input swept (~100 sites); inputCls retired; local/input-primitive
- useReturnFocus: an in-place editor hands the focus back to its trigger on
  Enter/Escape (the playlist and Plex title renames, the priority number);
  the Plex playlist rename gains Escape and an accessible name
- back to top: a round 48 FAB (owner decision); DESIGN.md A2 and the log

frontend/src/components/ui/form.tsx

@@ -5,15 +5,6 @@ import { FocusSafeButton } from "./FocusSafeButton";
 // Shared form/settings primitives, factored out of the many panels that each re-declared
 // them (Settings, Config, Stats, admin pages, Setup wizard). Visual contract unchanged.
 
-/** The ONE text/select/number input recipe (full-width, surface bg, rounded-lg, 2px accent focus
- * RING). R10 S3 unified every input onto this: the old settings-family border-focus style
- * (`bg-card rounded-xl focus:border-accent`) and its three copy-pasted local `inputCls` constants
- * (KeyGate/SettingsPanel/SetupWizard) are gone. Size variants (a small pager/table-filter/chat
- * input) keep their own width/radius/padding but adopt the same bg-surface + ring-focus look
- * inline — reach for this const for a default full-size field, match its look for a smaller one. */
-export const inputCls =
-  "w-full rounded-lg bg-surface border border-border px-3 py-2 text-sm focus:outline-hidden focus:ring-2 focus:ring-accent/40";
-
 /** Pill on/off switch — the bare control; compose it with your own label/row. Pass `label` for
  * the accessible name (the visible row text) since the control itself has no inner text. */
 export function Switch({