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/viewers/SchemaLinkingViewer.tsx

@@ -133,13 +133,13 @@ export function SchemaLinkingViewer({ linking }: { linking: SchemaLinking }) {
         <button
           onClick={() => setView("chart")}
           disabled={oversized}
-          className={view === "chart" ? "font-bold" : ""}
+          className={`rounded-md border border-border/70 px-2 py-1 text-xs shadow-xs transition-colors hover:bg-accent disabled:cursor-not-allowed disabled:opacity-50 ${view === "chart" ? "font-semibold" : ""}`}
         >
           Graph
         </button>
         <button
           onClick={() => setView("table")}
-          className={view === "table" ? "font-bold" : ""}
+          className={`rounded-md border border-border/70 px-2 py-1 text-xs shadow-xs transition-colors hover:bg-accent ${view === "table" ? "font-semibold" : ""}`}
         >
           Table
         </button>