style(theme): add dialog & panel CSS vars and refactor status panel styles

Add CSS custom properties for dialog backdrop, shadows, and panel
highlights to centralize visual theming. Refactor the status panel
overlay to consume these tokens and use color-mix instead of hardcoded
rgba values. This improves visual consistency and lets overlays adapt
cleanly to appearance changes and theme variants.

- Centralize dialog and panel visuals with new CSS variables
- Replace fixed rgba values with tokenized colors and color-mix
- Move borders, shadows, and gradients to use the new theme tokens

src/App.svelte

@@ -1179,7 +1179,8 @@
     root.dataset.appearance = next;
     const customProperties = [
       "--app-bg", "--app-button-bg", "--app-input-bg", "--app-dialog-bg", "--app-dialog-chrome",
-      "--app-settings-row-bg", "--color-surface", "--color-surface-alt", "--color-surface-dim",
+      "--app-dialog-backdrop", "--app-dialog-shadow", "--app-panel-shadow", "--app-settings-row-bg",
+      "--color-surface", "--color-surface-alt", "--color-surface-dim",
       "--color-surface-hover", "--color-surface-raised", "--color-surface-solid", "--color-border",
       "--color-border-subtle", "--color-border-input", "--color-primary", "--color-primary-dark",
       "--color-accent", "--color-ink", "--color-ink-muted", "--color-ink-faint", "--color-ink-dim",
@@ -1195,6 +1196,9 @@
       "--app-input-bg": `color-mix(in srgb, ${surface} 88%, white)`,
       "--app-dialog-bg": surface,
       "--app-dialog-chrome": `color-mix(in srgb, ${surface} 90%, ${background})`,
+      "--app-dialog-backdrop": `color-mix(in srgb, ${background} 72%, transparent)`,
+      "--app-dialog-shadow": `0 24px 68px color-mix(in srgb, ${text} 24%, transparent), 0 2px 12px color-mix(in srgb, ${text} 12%, transparent)`,
+      "--app-panel-shadow": `0 18px 48px color-mix(in srgb, ${text} 18%, transparent), inset 0 1px 0 color-mix(in srgb, ${surface} 88%, white)`,
       "--app-settings-row-bg": `color-mix(in srgb, ${surface} 92%, ${background})`,
       "--color-surface": surface,
       "--color-surface-alt": `color-mix(in srgb, ${surface} 82%, ${background})`,

src/lib/components/StatusPanel.svelte

@@ -660,8 +660,12 @@
     display: grid;
     place-items: center;
     background:
-      radial-gradient(circle at 50% 38%, rgba(111, 140, 255, 0.1), transparent 55%),
-      rgba(7, 10, 16, 0.62);
+      radial-gradient(
+        circle at 50% 38%,
+        color-mix(in srgb, var(--color-accent) 13%, transparent),
+        transparent 55%
+      ),
+      var(--app-dialog-backdrop);
     backdrop-filter: blur(4px);
     animation: status-panel-overlay-in 120ms ease;
   }
@@ -673,13 +677,13 @@
     gap: 12px;
     width: min(300px, calc(100% - 32px));
     padding: 26px 28px 26px;
-    border: 1px solid rgba(90, 111, 154, 0.28);
+    border: 1px solid var(--color-border-input);
     border-radius: 16px;
     background:
-      linear-gradient(180deg, rgba(23, 29, 43, 0.92), rgba(12, 17, 27, 0.94)),
-      var(--color-surface-raised);
+      var(--app-panel-highlight),
+      var(--app-dialog-bg);
     color: var(--color-ink);
-    box-shadow: 0 18px 44px rgba(0, 0, 0, 0.34), inset 0 1px 0 rgba(255, 255, 255, 0.05);
+    box-shadow: var(--app-dialog-shadow);
   }
 
   .status-panel-overlay-mark {
@@ -694,7 +698,7 @@
   .status-panel-overlay-halo {
     position: absolute;
     inset: 6px;
-    border: 1px solid rgba(111, 140, 255, 0.22);
+    border: 1px solid color-mix(in srgb, var(--color-primary) 34%, transparent);
     border-radius: 22px;
     transform: rotate(45deg);
   }
@@ -703,7 +707,7 @@
   }
   .status-panel-overlay-halo.halo-two {
     inset: 16px;
-    border-color: rgba(77, 182, 214, 0.24);
+    border-color: color-mix(in srgb, var(--color-accent) 38%, transparent);
     animation: status-panel-overlay-halo-breathe 2.4s ease-in-out infinite reverse;
   }
 
@@ -721,16 +725,16 @@
     stroke-linecap: round;
     stroke-dasharray: 165;
     stroke-dashoffset: 165;
-    filter: drop-shadow(0 0 6px rgba(77, 182, 214, 0.32));
+    filter: drop-shadow(0 0 6px color-mix(in srgb, var(--color-accent) 38%, transparent));
     animation: status-panel-overlay-trace-draw 2.6s ease-in-out infinite;
   }
-  .status-panel-overlay-traces .trace-main { stroke: #6f8cff; }
+  .status-panel-overlay-traces .trace-main { stroke: var(--color-primary); }
   .status-panel-overlay-traces .trace-branch {
-    stroke: #4db6d6;
+    stroke: var(--color-accent);
     animation-delay: 0.28s;
   }
   .status-panel-overlay-traces .trace-cut {
-    stroke: rgba(177, 186, 208, 0.42);
+    stroke: color-mix(in srgb, var(--color-ink-muted) 52%, transparent);
     stroke-dasharray: 128;
     stroke-dashoffset: 128;
     animation-delay: 0.55s;
@@ -743,8 +747,8 @@
     height: 64px;
     object-fit: contain;
     filter:
-      drop-shadow(0 8px 12px rgba(0, 0, 0, 0.5))
-      drop-shadow(0 0 10px rgba(77, 182, 214, 0.2));
+      drop-shadow(0 8px 12px color-mix(in srgb, var(--color-ink) 24%, transparent))
+      drop-shadow(0 0 10px color-mix(in srgb, var(--color-accent) 24%, transparent));
     animation: status-panel-overlay-icon-float 2.4s ease-in-out infinite;
   }
 
@@ -765,15 +769,16 @@
     height: 4px;
     overflow: hidden;
     border-radius: 999px;
-    background: rgba(111, 140, 255, 0.14);
+    border: 1px solid var(--color-border-subtle);
+    background: color-mix(in srgb, var(--color-primary) 12%, var(--color-surface-dim));
   }
   .status-panel-overlay-bar span {
     position: absolute;
     inset: 0;
     width: 46%;
     border-radius: inherit;
-    background: linear-gradient(90deg, transparent, #6f8cff 40%, #4db6d6 74%, transparent);
-    box-shadow: 0 0 12px rgba(77, 182, 214, 0.26);
+    background: linear-gradient(90deg, transparent, var(--color-primary) 40%, var(--color-accent) 74%, transparent);
+    box-shadow: 0 0 12px color-mix(in srgb, var(--color-accent) 32%, transparent);
     animation: status-panel-overlay-bar-slide 1.35s ease-in-out infinite;
   }