fix(lab): stabilize recorded spatial playback

apps/control-station/src/styles/m4-replay-threat.css

@@ -12,6 +12,48 @@
   background: var(--nodedc-canvas);
 }
 
+.m4-replay-threat-visual__deck,
+.m4-replay-threat-visual__layer {
+  position: absolute;
+  inset: 0;
+  width: 100%;
+  height: 100%;
+  min-width: 0;
+  min-height: 0;
+}
+
+.m4-replay-threat-visual__layer {
+  visibility: hidden;
+  opacity: 0;
+  pointer-events: none;
+}
+
+.m4-replay-threat-visual__layer[data-active="true"] {
+  z-index: 1;
+  visibility: visible;
+  opacity: 1;
+  pointer-events: auto;
+}
+
+.m4-replay-threat-visual__buffering {
+  position: absolute;
+  z-index: 5;
+  top: 4.9rem;
+  left: 50%;
+  display: flex;
+  align-items: center;
+  gap: 0.4rem;
+  border: 1px solid var(--nodedc-glass-outline);
+  border-radius: var(--nodedc-radius-control-compact);
+  background: var(--nodedc-floating-surface);
+  padding: 0.42rem 0.58rem;
+  color: var(--nodedc-text-secondary);
+  font-size: 0.54rem;
+  backdrop-filter: blur(var(--nodedc-blur-control));
+  pointer-events: none;
+  transform: translateX(-50%);
+}
+
 .laboratory-metric-evidence-scene__viewport {
   position: absolute;
   inset: 0;