style(frontend): look&feel v2 — layered shadows, sharper radii, mono data register

Colors (GSD palette) untouched. New visual vocabulary across the whole GUI:
- warm-tinted layered shadow tokens (--shadow-xs/sm/md) replacing flat rings;
  cards/dialogs framed with hairline border + real elevation
- strict radii scale: xl cards / lg inputs / md controls / 2xl dialogs;
  buttons move from pills to rounded-md
- third type register: --font-mono + tabular-nums on SQL, timers, dates, ids;
  standardized .thot-label micro-label tier
- prose: framed tables with uppercase headers, elevated code blocks
- SqlViewer badges moved from hardcoded Tailwind greens/reds to success/
  destructive token tints; ResultsPanel inline styles replaced with classes
- artifact gate: first option rendered as filled primary action

Verified offline via Playwright against a mock backend replaying a real psd
session (no VPN needed). tsc clean, 115/115 vitest.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

frontend/src/widgets/FallbackWidget.tsx

@@ -4,11 +4,11 @@ import type { WidgetProps } from "./types";
 export function FallbackWidget({ descriptor, onRespond }: WidgetProps) {
   const [text, setText] = useState("");
   return (
-    <div className="border rounded p-3 space-y-2">
+    <div className="rounded-xl border border-border/70 bg-card p-3 shadow-sm space-y-2">
       <p className="text-sm text-amber-600">Unsupported widget (kind: {descriptor.widget}) — respond manually</p>
-      <pre className="text-xs overflow-auto max-h-48 bg-muted p-2">{JSON.stringify(descriptor, null, 2)}</pre>
-      <textarea className="w-full border rounded p-1" value={text} onChange={(e) => setText(e.target.value)} />
-      <button className="border rounded px-2 py-1" onClick={() => onRespond({ id: descriptor.id, control: "freetext", text })}>Send</button>
+      <pre className="text-xs font-mono overflow-auto max-h-48 rounded-lg bg-muted p-2">{JSON.stringify(descriptor, null, 2)}</pre>
+      <textarea className="w-full rounded-lg border border-input bg-card p-2 text-sm shadow-xs outline-none transition-[border-color,box-shadow] focus:border-primary/50 focus:ring-2 focus:ring-ring/20" value={text} onChange={(e) => setText(e.target.value)} />
+      <button className="rounded-md border border-border/70 px-2 py-1 text-sm shadow-xs transition-colors hover:bg-accent" onClick={() => onRespond({ id: descriptor.id, control: "freetext", text })}>Send</button>
     </div>
   );
 }