a11y: update theme tokens and global styles for WCAG AAA

src/app.css

@@ -5,17 +5,19 @@
   --color-surface: #0e0e0e;
   --color-card: #141414;
   --color-card-lt: #1c1c1c;
-  --color-border: #222222;
+  --color-border: #3a3a3a;
   --color-accent: #ff4d00;
   --color-accent-lt: #ff7733;
   --color-accent-dim: #ff4d0018;
   --color-accent-glow: #ff4d0040;
   --color-success: #3fb950;
   --color-warning: #f0a500;
-  --color-danger: #f85149;
+  --color-danger: #ff6b6b;
   --color-text-pri: #ffffff;
-  --color-text-sec: #8a8a8a;
-  --color-text-dim: #3a3a3a;
+  --color-text-sec: #a8a8a8;
+  --color-text-dim: #5c5c5c;
+  --color-input-border: #444444;
+  --color-surface-lt: #1e1e1e;
   --color-caption-bg: #050505;
 }
 
@@ -30,6 +32,11 @@ body {
     Arial, sans-serif;
   overflow: hidden;
   height: 100%;
+  line-height: 1.625;
+}
+
+[data-tauri-drag-region],
+[data-tauri-drag-region] * {
   user-select: none;
   -webkit-user-select: none;
 }
@@ -69,10 +76,31 @@ body {
   border-width: 0;
 }
 
+/* ── Accessibility: Skip link ── */
+.skip-link {
+  position: absolute;
+  top: -100%;
+  left: 50%;
+  transform: translateX(-50%);
+  z-index: 10000;
+  padding: 8px 16px;
+  background: var(--color-accent);
+  color: #000;
+  font-size: 13px;
+  font-weight: 600;
+  border-radius: 0 0 8px 8px;
+  text-decoration: none;
+  transition: top 0.15s ease;
+}
+.skip-link:focus {
+  top: 0;
+}
+
 /* ── Accessibility: Focus indicators ── */
 :focus-visible {
   outline: 2px solid var(--color-accent);
   outline-offset: 2px;
+  box-shadow: 0 0 0 4px rgba(255, 255, 255, 0.3);
 }
 
 /* ── Accessibility: Reduced motion ── */