Add generationStatus and match3d/runtime fixes

Introduce persistent generationStatus to work summaries (puzzle & match3d) and propagate generation recovery rules across docs and frontend/backends so "generating" is restored from server-side work summary rather than ephemeral front-end notices. Update API server image/asset handling (improve match3d material sheet green/alpha decontamination and promote generatedItemAssets background fields) and add runtime improvements: alpha-based hotspot hit-testing, tray insertion/three-match animation behavior, and session re-read on client-side VectorEngine timeouts/lock-screen interruptions. Many docs, tests and related frontend modules updated/added to reflect these contract and behavior changes.

src/index.css

@@ -281,8 +281,124 @@ body {
   will-change: transform, opacity;
 }
 
+@keyframes match3d-tray-token-shift {
+  0% {
+    transform: translate3d(
+      var(--match3d-tray-shift-x, 0px),
+      var(--match3d-tray-shift-y, 0px),
+      0
+    );
+  }
+
+  100% {
+    transform: translate3d(0, 0, 0);
+  }
+}
+
+.match3d-tray-token-shift {
+  animation: match3d-tray-token-shift 0.24s cubic-bezier(0.2, 0.8, 0.2, 1)
+    both;
+  will-change: transform;
+}
+
+@keyframes match3d-tray-token-clear {
+  0% {
+    opacity: 1;
+    transform: translate3d(-50%, -50%, 0) scale(1);
+  }
+
+  62% {
+    opacity: 1;
+    transform:
+      translate3d(
+        calc(-50% + var(--match3d-tray-clear-dx, 0px)),
+        calc(-50% + var(--match3d-tray-clear-dy, 0px)),
+        0
+      )
+      scale(0.84);
+  }
+
+  100% {
+    opacity: 0;
+    transform:
+      translate3d(
+        calc(-50% + var(--match3d-tray-clear-dx, 0px)),
+        calc(-50% + var(--match3d-tray-clear-dy, 0px)),
+        0
+      )
+      scale(0.38);
+    filter: blur(1px);
+  }
+}
+
+.match3d-tray-token-clear {
+  transform: translate3d(-50%, -50%, 0);
+  animation: match3d-tray-token-clear 0.46s cubic-bezier(0.2, 0.72, 0.18, 1)
+    both;
+  transform-origin: center;
+  will-change: transform, opacity;
+}
+
+@keyframes match3d-tray-clear-flash {
+  0% {
+    opacity: 0;
+    transform: translate(-50%, -50%) scale(0.2);
+  }
+
+  42% {
+    opacity: 0.95;
+  }
+
+  100% {
+    opacity: 0;
+    transform: translate(-50%, -50%) scale(1.45);
+  }
+}
+
+.match3d-tray-clear-flash {
+  width: 4rem;
+  height: 4rem;
+  border-radius: 9999px;
+  background:
+    radial-gradient(circle, rgba(255, 255, 255, 0.95) 0 10%, transparent 12%),
+    radial-gradient(circle, rgba(255, 236, 157, 0.48) 0 42%, transparent 64%);
+  box-shadow:
+    0 0 22px rgba(255, 255, 255, 0.62),
+    0 0 52px rgba(251, 191, 36, 0.34);
+  mix-blend-mode: screen;
+  animation: match3d-tray-clear-flash 0.46s ease-out both;
+  transform: translate(-50%, -50%);
+}
+
+@keyframes match3d-merge-feedback-pulse {
+  0% {
+    opacity: 0;
+    transform: scale(0.48);
+  }
+
+  42% {
+    opacity: 0.8;
+  }
+
+  100% {
+    opacity: 0;
+    transform: scale(1.28);
+  }
+}
+
+.match3d-merge-feedback-pulse {
+  animation: match3d-merge-feedback-pulse 0.52s ease-out both;
+  background:
+    radial-gradient(circle, rgba(255, 255, 255, 0.56) 0 18%, transparent 20%),
+    radial-gradient(circle, rgba(255, 255, 255, 0.28) 0 45%, transparent 68%);
+}
+
 @media (prefers-reduced-motion: reduce) {
-  .match3d-token-fly-to-tray {
+  .match3d-token-fly-to-tray,
+  .match3d-tray-token-shift,
+  .match3d-tray-token-clear,
+  .match3d-tray-clear-flash,
+  .match3d-merge-feedback-pulse {
     animation-duration: 1ms;
   }
 }