feat(ui): "Graphite & Honey" redesign — warm dark, monospace-first

- new design system in globals.css: warm graphite surfaces, ivory text, honey
  accent; semantic status/data-type/syntax tokens replacing hardcoded colors
- IBM Plex Mono as the universal UI font (sans + mono), tabular numerals
- custom CodeMirror SQL theme (src/lib/editor-theme.ts) matching the palette
- data grid: zebra striping + honey row hover, stronger sticky header
- route status dots, JSON syntax, EXPLAIN cost, schema-tree icons and the
  read/write toggle through the new tokens
- TUSK wordmark in the toolbar

src/components/layout/Toolbar.tsx

@@ -66,6 +66,15 @@ export function Toolbar() {
           "--strip-color": activeColor ?? "transparent",
         } as React.CSSProperties}
       >
+        <span
+          className="tusk-wordmark select-none px-1 text-[12px] text-primary"
+          style={{ textShadow: "0 0 10px oklch(0.808 0.124 82 / 35%)" }}
+        >
+          TUSK
+        </span>
+
+        <div className="mx-1 h-4 w-px bg-border" />
+
         <Button
           variant="ghost"
           size="xs"