Implement Phase 1 audio gaps: 20 quick-win procedural sounds and ambient loops

- 18 low + 2 low-medium discrete elements (comm badge, door swishes, bosun
  whistle, sickbay ECG, TARDIS lever/door, Sevastopol sparks, commlock tone,
  station ECG, solar roar, cryo sigh, Orion thump, tea dispenser, kettle
  whistle, plaid alarm, cassette transport, grappler servo, radio static,
  mag-boot latch) with soundboard buttons, preset tuning, and automated
  background loops
- bio-wraith misty life-support tuning; sound_reference.md and audio_gaps.md
  implementation tracking
- gitignore audition scratch and local artifacts

css/style.css

@@ -341,6 +341,62 @@ body {
   color: #fff;
 }
 
+/* Master Engage / Full Stop Play Button */
+#btn-master-play {
+  background: #00cc66;
+  color: #000000;
+  box-shadow: 0 0 12px rgba(0, 204, 102, 0.45);
+  transition: transform 0.1s, filter 0.15s, background-color 0.2s, box-shadow 0.2s;
+}
+
+#btn-master-play:hover {
+  filter: brightness(1.2);
+}
+
+#btn-master-play.playing {
+  background: #ff3333;
+  color: #ffffff;
+  box-shadow: 0 0 14px rgba(255, 51, 51, 0.5);
+}
+
+#btn-master-play.engaging {
+  animation: lcars-engage-flash 0.35s infinite alternate ease-in-out;
+}
+
+#btn-master-play.stopping {
+  animation: lcars-stop-flash 0.35s infinite alternate ease-in-out;
+}
+
+@keyframes lcars-engage-flash {
+  0% {
+    background: #00cc66;
+    color: #000000;
+    box-shadow: 0 0 6px rgba(0, 204, 102, 0.4);
+    filter: brightness(0.95);
+  }
+  100% {
+    background: #33ff99;
+    color: #000000;
+    box-shadow: 0 0 24px rgba(0, 255, 136, 0.95);
+    filter: brightness(1.35);
+  }
+}
+
+@keyframes lcars-stop-flash {
+  0% {
+    background: #ff3333;
+    color: #ffffff;
+    box-shadow: 0 0 6px rgba(255, 51, 51, 0.4);
+    filter: brightness(0.95);
+  }
+  100% {
+    background: #ff6666;
+    color: #ffffff;
+    box-shadow: 0 0 24px rgba(255, 51, 51, 0.95);
+    filter: brightness(1.35);
+  }
+}
+
 /* Action Pill Buttons */
 .pill-button-group {
   display: flex;