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/InfoWidget.tsx

@@ -1,5 +1,5 @@
 import type { WidgetProps } from "./types";
 export function InfoWidget({ descriptor }: WidgetProps) {
   const color = descriptor.level === "error" ? "text-red-600" : descriptor.level === "warning" ? "text-amber-600" : "text-foreground";
-  return <p className={`text-sm ${color}`}>{descriptor.text ?? descriptor.title}</p>;
+  return <p className={`text-sm leading-relaxed ${color}`}>{descriptor.text ?? descriptor.title}</p>;
 }