fix: drag & drop corrigé — 3 bugs critiques résolus

1. types.includes → Array.from(types).includes (DOMStringList n'a pas .includes)
2. dragleave: compteur _dragCounter empêche clear sur child enter/leave
3. drag-to-split: zone recalculée dans drop handler (plus de closure corrompue)
4. drop: stopPropagation + skip same-paneId dans container handler
5. dragenter: appel preventDefault pour accepter le drop dès l'entrée

frontend/js/pane-manager.js

@@ -734,11 +734,18 @@ const PaneManager = {
 
   /** Add dragover/drop on a pane container for cross-pane transfers + drag-to-split */
   _setupPaneDropZone(container, paneId) {
-    let _edgeZone = null; // 'right' | 'bottom' | null
+    let _dragCounter = 0;
+
+    container.addEventListener('dragenter', (e) => {
+      const types = Array.from(e.dataTransfer.types || []);
+      if (!types.includes('application/obsigate-tab')) return;
+      _dragCounter++;
+      e.preventDefault();
+    });
 
     container.addEventListener('dragover', (e) => {
-      const raw = e.dataTransfer.types.includes('application/obsigate-tab');
-      if (!raw) return;
+      const types = Array.from(e.dataTransfer.types || []);
+      if (!types.includes('application/obsigate-tab')) return;
       e.preventDefault();
       e.dataTransfer.dropEffect = 'move';
 
@@ -750,37 +757,35 @@ const PaneManager = {
 
       // Clean up previous indicators
       container.querySelectorAll('.pane-drop-zone-indicator').forEach(d => d.remove());
-      _edgeZone = null;
+      const tabBar = container.querySelector('.tab-bar');
+      if (tabBar) tabBar.classList.remove('drop-target');
 
-      if (isSingle) {
-        if (relX > rect.width * 0.75) {
-          _edgeZone = 'right';
-        } else if (relY > rect.height * 0.75) {
-          _edgeZone = 'bottom';
-        }
-      }
-
-      if (_edgeZone) {
-        // Show edge zone indicator
+      if (isSingle && relX > rect.width * 0.72) {
         const indicator = document.createElement('div');
-        indicator.className = 'pane-drop-zone-indicator pane-drop-zone-' + _edgeZone;
+        indicator.className = 'pane-drop-zone-indicator pane-drop-zone-right';
+        container.appendChild(indicator);
+      } else if (isSingle && relY > rect.height * 0.72) {
+        const indicator = document.createElement('div');
+        indicator.className = 'pane-drop-zone-indicator pane-drop-zone-bottom';
         container.appendChild(indicator);
       } else {
         // Show tab-bar highlight for cross-pane transfer
-        const tabBar = container.querySelector('.tab-bar');
         if (tabBar) tabBar.classList.add('drop-target');
       }
     });
 
     container.addEventListener('dragleave', (e) => {
+      _dragCounter--;
+      if (_dragCounter > 0) return; // Still inside container (entered a child)
       container.querySelectorAll('.pane-drop-zone-indicator').forEach(d => d.remove());
       const tabBar = container.querySelector('.tab-bar');
       if (tabBar) tabBar.classList.remove('drop-target');
-      _edgeZone = null;
     });
 
     container.addEventListener('drop', (e) => {
       e.preventDefault();
+      e.stopPropagation();
+      _dragCounter = 0;
       container.querySelectorAll('.pane-drop-zone-indicator').forEach(d => d.remove());
       const tabBar = container.querySelector('.tab-bar');
       if (tabBar) tabBar.classList.remove('drop-target');
@@ -789,28 +794,33 @@ const PaneManager = {
       if (!raw) return;
       try {
         const dragData = JSON.parse(raw);
+        if (dragData.paneId === paneId) return; // Same pane, let tab handler deal with it
 
-        if (_edgeZone === 'right') {
-          // Drag to right edge → split right with this tab
+        // Recalculate edge zone from drop coordinates
+        const rect = container.getBoundingClientRect();
+        const relX = e.clientX - rect.left;
+        const relY = e.clientY - rect.top;
+        const isSingle = !this.isSplit();
+
+        if (isSingle && relX > rect.width * 0.72) {
+          // Dropped on right edge → split right with this tab
           this.splitRight();
-          // Transfer the dragged tab to the new pane
           setTimeout(() => {
             const newPaneId = this.panes.length - 1;
             this.transferTab(dragData.paneId, dragData.tabId, newPaneId);
-          }, 100);
-        } else if (_edgeZone === 'bottom') {
-          // Drag to bottom edge → split down with this tab
+          }, 150);
+        } else if (isSingle && relY > rect.height * 0.72) {
+          // Dropped on bottom edge → split down with this tab
           this.splitDown();
           setTimeout(() => {
             const newPaneId = this.panes.length - 1;
             this.transferTab(dragData.paneId, dragData.tabId, newPaneId);
-          }, 100);
-        } else if (dragData.paneId !== paneId) {
-          // Cross-pane transfer (dropped on tab bar or content area of another pane)
+          }, 150);
+        } else {
+          // Cross-pane transfer (dropped on tab bar or empty area of another pane)
           this.transferTab(dragData.paneId, dragData.tabId, paneId);
         }
       } catch (e2) { /* ignore */ }
-      _edgeZone = null;
     });
   },