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/design-lab/DesignLab.tsx

@@ -4,6 +4,7 @@ import { BatchA } from "./batchA";
 import { BatchB } from "./batchB";
 import { BatchC } from "./batchC";
 import { Chip } from "../components/ui/Chip";
+import { Slider } from "../components/ui/NativeControls";
 
 // The design lab (E28): the living style guide. Dev-only — see main.tsx and devOnlyGuard.ts. It sits
 // OUTSIDE <App>, so it owns the theme attributes on <html> itself, through the same data-theme /
@@ -59,14 +60,13 @@ export default function DesignLab() {
         </Chip>
         <label className="flex items-center gap-2 text-xs text-muted">
           text {look.fontScale.toFixed(2)}
-          <input
-            type="range"
+          <Slider
+            className="w-24"
             min={0.9}
             max={1.2}
             step={0.02}
             value={look.fontScale}
-            onChange={(e) => set({ fontScale: Number(e.target.value) })}
-            className="w-24 accent-accent"
+            onChange={(v) => set({ fontScale: v })}
           />
         </label>
         <nav className="flex flex-wrap gap-1 text-xs">