fix: drag-drop utilise text/plain uniquement + logs console

- dragstart: setData 'text/plain' (universel, pas de custom MIME)
- drop container + tab: getData('text/plain')
- console.log dans le drop handler pour diagnostic
- Suppression application/obsigate-tab (non fiable cross-browser)

frontend/js/pane-manager.js

@@ -371,8 +371,8 @@ function createPaneTabManager(paneId) {
           const payload = JSON.stringify({
             paneId: this.paneId, tabId: tab.id, index: idx
           });
-          e.dataTransfer.setData('application/obsigate-tab', payload);
+          // text/plain is universally supported across all browsers for drag-drop
-          e.dataTransfer.setData('text/plain', payload); // fallback for browser compat
+          e.dataTransfer.setData('text/plain', payload);
           e.dataTransfer.effectAllowed = 'move';
           el.classList.add('dragging');
         });
@@ -395,9 +395,9 @@ function createPaneTabManager(paneId) {
           e.preventDefault();
           e.stopPropagation(); // Prevent container handler from double-firing
           document.querySelectorAll('.tab-drop-indicator').forEach(d => d.remove());
-          try {
+          const raw = e.dataTransfer.getData('text/plain');
-            const raw = e.dataTransfer.getData('application/obsigate-tab');
           if (!raw) return;
+          try {
             const dragData = JSON.parse(raw);
             // Same pane — reorder
             if (dragData.paneId === this.paneId) {
@@ -796,14 +796,14 @@ const PaneManager = {
       const tabBar = container.querySelector('.tab-bar');
       if (tabBar) tabBar.classList.remove('drop-target');
 
-      // Try both data formats
+      // Get drag data (text/plain is universally supported)
-      let raw = e.dataTransfer.getData('application/obsigate-tab');
+      const raw = e.dataTransfer.getData('text/plain');
-      if (!raw) raw = e.dataTransfer.getData('text/plain');
+      console.log('[PaneManager] drop fired, raw data:', raw ? raw.substring(0, 80) : 'null');
-      if (!raw) return;
 
-      try {
+      if (!raw) return;
-        const dragData = JSON.parse(raw);
+      let dragData;
-        if (dragData.paneId == null || dragData.tabId == null) return;
+      try { dragData = JSON.parse(raw); } catch (e2) { console.log('[PaneManager] JSON parse error:', e2); return; }
+      if (dragData.paneId == null || dragData.tabId == null) { console.log('[PaneManager] missing paneId/tabId'); return; }
 
       // Recalculate edge zone from drop coordinates
       const rect = container.getBoundingClientRect();
@@ -811,24 +811,34 @@ const PaneManager = {
       const relY = e.clientY - rect.top;
       const isSingle = !this.isSplit();
 
+      console.log('[PaneManager] drop at', relX.toFixed(0), relY.toFixed(0),
+        'rect', rect.width.toFixed(0), 'x', rect.height.toFixed(0),
+        'isSingle', isSingle, 'paneId', paneId, 'srcPane', dragData.paneId);
+
       if (isSingle && relX > rect.width * 0.72) {
+        console.log('[PaneManager] → splitRight');
         this.splitRight();
-          setTimeout(() => {
+        // Transfer after DOM settles
+        const transfer = () => {
           const newPaneId = this.panes.length - 1;
+          console.log('[PaneManager] transferring tab', dragData.tabId, 'to pane', newPaneId);
           this.transferTab(dragData.paneId, dragData.tabId, newPaneId);
-          }, 200);
+        };
+        setTimeout(transfer, 200);
       } else if (isSingle && relY > rect.height * 0.72) {
+        console.log('[PaneManager] → splitDown');
         this.splitDown();
-          setTimeout(() => {
+        const transfer = () => {
           const newPaneId = this.panes.length - 1;
           this.transferTab(dragData.paneId, dragData.tabId, newPaneId);
-          }, 200);
+        };
+        setTimeout(transfer, 200);
       } else if (dragData.paneId !== paneId) {
-          // Cross-pane transfer (already in split mode, different panes)
+        console.log('[PaneManager] → cross-pane transfer', dragData.paneId, '→', paneId);
         this.transferTab(dragData.paneId, dragData.tabId, paneId);
+      } else {
+        console.log('[PaneManager] → same pane, no edge — letting tab handler deal');
       }
-        // else: same pane, not edge — tab handler deals with reorder
-      } catch (e2) { console.debug('PaneManager drop error:', e2); }
     });
   },