feat: refactor queue panel and split layout with deferred reveal and pointer events

- Add PointerEvent support for queue toggle, edge drag, and splitter interactions
- Implement deferred queue panel reveal animation (mr-queue-opening class)
- Make queue panel updates demand-driven; skip refresh when panel is hidden
- Replace per-item remove listeners with event delegation on queue list
- Track queue split container width via ResizeObserver with safe fallbacks
- Centralize split flex application and persist queue width/collapsed state with debounce
- Fix missing browser split pane styles to use helper-track CSS variables
- Add deferred UI cleanup for missing browser split drag end
- Add prewarm frame fallback when ResizeObserver is unavailable

web/css/resolver-shell.css

@@ -179,16 +179,19 @@
     padding: 8px 6px 6px;
     flex: 1;
     min-height: 0;
+    min-width: 0;
     align-items: stretch;
     position: relative;
+    overflow: hidden;
     background: var(--mr-bg, #121212);
 }
 
 #model-resolver-content {
     overflow-y: auto;
-    flex: 1;
+    flex: 1 1 0;
     min-height: 0;
-    contain: layout paint style;
+    min-width: 0;
+    contain: size layout paint style;
     background: var(--mr-bg, #222);
 }
 
@@ -196,14 +199,34 @@
     width: 320px;
     min-width: 240px;
     max-width: 70%;
+    flex: 0 0 320px;
+    box-sizing: border-box;
     display: flex;
     flex-direction: column;
     padding-left: 0;
     border-left: 0;
-    contain: layout paint style;
+    contain: size layout paint style;
     background: var(--mr-bg, #121212);
 }
 
+#model-resolver-queue.mr-queue-opening .mr-queue-stack {
+    content-visibility: hidden;
+    contain-intrinsic-size: 320px 420px;
+}
+
+#model-resolver-body.mr-queue-opening-layout #model-resolver-queue {
+    position: absolute;
+    top: 8px;
+    right: 6px;
+    bottom: 6px;
+    z-index: 998;
+    box-shadow: -12px 0 24px rgba(0, 0, 0, 0.24);
+}
+
+#model-resolver-body.mr-queue-opening-layout #model-resolver-splitter {
+    display: none !important;
+}
+
 #model-resolver-body.mr-is-resizing-queue #model-resolver-content,
 #model-resolver-body.mr-is-resizing-queue #model-resolver-queue {
     pointer-events: none;
@@ -292,6 +315,7 @@
     display: flex;
     flex-direction: column;
     min-height: 0;
+    min-width: 0;
     flex: 1 1 auto;
 }