fix resize: use pointer capture to handle drag over iframe

When dragging the resize handle rightward to narrow the panel, the
mouse cursor moved over the iframe which captured mouse events.
document-level mousemove stopped firing, making narrowing impossible.

Fix: replace mouse events with pointer events + setPointerCapture.
The handle element captures ALL pointer events during drag regardless
of where the cursor moves (over iframe, outside window, etc).
Applied to both local_workspace.html and library.html.

app/templates/library.html

@@ -1280,20 +1280,21 @@ function libraryPage() {
   var handle = document.getElementById('lib-peek-resize-handle');
   if (!panel || !handle) return;
   var startX, startWidth, dragging = false;
-  handle.addEventListener('mousedown', function(e) {
+  handle.addEventListener('pointerdown', function(e) {
     e.preventDefault();
+    handle.setPointerCapture(e.pointerId);
     startX = e.clientX;
     startWidth = panel.offsetWidth;
     dragging = true;
     document.body.style.userSelect = 'none';
   });
-  document.addEventListener('mousemove', function(e) {
+  handle.addEventListener('pointermove', function(e) {
     if (!dragging) return;
     var deltaX = startX - e.clientX;
     var newWidth = Math.max(300, Math.min(window.innerWidth * 0.9, startWidth + deltaX));
     panel.style.width = newWidth + 'px';
   });
-  document.addEventListener('mouseup', function(e) {
+  handle.addEventListener('pointerup', function(e) {
     if (!dragging) return;
     document.body.style.userSelect = '';
     var moved = Math.abs(e.clientX - startX);
@@ -1303,6 +1304,7 @@ function libraryPage() {
     }
     dragging = false;
     try { localStorage.setItem('fd_peek_width', panel.style.width); } catch(ex) {}
+    handle.releasePointerCapture(e.pointerId);
   });
   try {
     var saved = localStorage.getItem('fd_peek_width');

app/templates/local_workspace.html

@@ -639,20 +639,21 @@ window._wsInitData = (function() {
       var handle = document.getElementById('ws-preview-resize-handle');
       if (!panel || !handle) return;
       var startX, startWidth, dragging = false;
-      handle.addEventListener('mousedown', function(e) {
+      handle.addEventListener('pointerdown', function(e) {
         e.preventDefault();
+        handle.setPointerCapture(e.pointerId);
         startX = e.clientX;
         startWidth = panel.offsetWidth;
         dragging = true;
         document.body.style.userSelect = 'none';
       });
-      document.addEventListener('mousemove', function(e) {
+      handle.addEventListener('pointermove', function(e) {
         if (!dragging) return;
         var deltaX = startX - e.clientX;
         var newWidth = Math.max(300, Math.min(window.innerWidth * 0.9, startWidth + deltaX));
         panel.style.width = newWidth + 'px';
       });
-      document.addEventListener('mouseup', function(e) {
+      handle.addEventListener('pointerup', function(e) {
         if (!dragging) return;
         document.body.style.userSelect = '';
         var moved = Math.abs(e.clientX - startX);
@@ -661,6 +662,7 @@ window._wsInitData = (function() {
         }
         dragging = false;
         try { localStorage.setItem('fd_peek_width', panel.style.width); } catch(ex) {}
+        handle.releasePointerCapture(e.pointerId);
       });
       try {
         var saved = localStorage.getItem('fd_peek_width');