feat: guard missing-browser split drag and register CSS track property

web/css/resolver-main.css

@@ -444,6 +444,12 @@
     color: var(--mr-text-muted);
 }
 
+@property --mr-missing-detail-track {
+    syntax: "<length-percentage>";
+    inherits: false;
+    initial-value: 42%;
+}
+
 .mr-missing-browser {
     --mr-missing-bg: #111;
     --mr-missing-surface: rgba(255,255,255,0.03);

web/resolver/views/missing_browser_methods.js

@@ -504,6 +504,7 @@ export const missingBrowserMethods = {
         const nextWidth = this._missingBrowserSplitStart.width - (event.clientX - this._missingBrowserSplitStart.x);
         const bounds = this._missingBrowserSplitStart.bounds;
         this._pendingMissingBrowserSplitWidth = Math.round(Math.max(bounds.min, Math.min(bounds.max, nextWidth)));
+        if (this._pendingMissingBrowserSplitWidth === this._appliedMissingBrowserSplitWidth) return;
         const now = performance.now();
         if (this._lastMissingBrowserSplitApply && now - this._lastMissingBrowserSplitApply < 33) return;
         this._lastMissingBrowserSplitApply = now;