feat(gui): add time GUI

Co-authored-by: Copilot <copilot@github.com>

css/style.css

@@ -15,6 +15,10 @@ canvas {
   display: block;
 }
 
+.canvas-stage {
+  position: relative;
+}
+
 .maze-layout {
   width: min(1100px, calc(100vw - 24px));
   margin: 12px auto 20px;
@@ -44,6 +48,36 @@ canvas {
   height: min(62vh, 680px);
 }
 
+.canvas-hud {
+  position: absolute;
+  top: 14px;
+  left: 14px;
+  z-index: 2;
+  padding: 10px 12px;
+  border-radius: 12px;
+  background: rgba(6, 10, 15, 0.72);
+  border: 1px solid rgba(121, 174, 242, 0.3);
+  backdrop-filter: blur(8px);
+  box-shadow: 0 10px 24px rgba(0, 0, 0, 0.28);
+  pointer-events: none;
+}
+
+.canvas-hud-label {
+  font-size: 10px;
+  letter-spacing: 0.14em;
+  text-transform: uppercase;
+  color: #93a4b8;
+  margin-bottom: 4px;
+}
+
+.canvas-hud-value {
+  font-size: 22px;
+  font-weight: 700;
+  line-height: 1;
+  color: #eef5ff;
+  text-shadow: 0 0 12px rgba(121, 174, 242, 0.35);
+}
+
 .control-panel {
   padding: 16px;
   overflow-y: auto;