fix: split view — plus de panneaux vides, transfert auto de l'onglet

- _hasAnyTab(): empêche split si aucun onglet ouvert (tous les points d'entrée)
- _copyActiveTabToNewPane(): copie l'onglet actif dans le nouveau panneau
- Menu contextuel: l'onglet cliqué-droit est transféré dans le nouveau panneau
- Raccourci clavier Ctrl+Alt+\: transfert l'onglet actif dans le nouveau panneau
- Boutons split: vérifient _hasAnyTab() avant d'agir
- Singleton ui.js: même comportement (split + transfert de l'onglet)

frontend/js/pane-manager.js

@@ -69,11 +69,11 @@ function createPaneTabManager(paneId) {
       `;
       btns.querySelector('[data-action="split-right"]').addEventListener('click', (e) => {
         e.stopPropagation();
-        if (window.PaneManager) window.PaneManager.splitRight();
+        if (window.PaneManager && window.PaneManager._hasAnyTab()) window.PaneManager.splitRight();
       });
       btns.querySelector('[data-action="split-down"]').addEventListener('click', (e) => {
         e.stopPropagation();
-        if (window.PaneManager) window.PaneManager.splitDown();
+        if (window.PaneManager && window.PaneManager._hasAnyTab()) window.PaneManager.splitDown();
       });
       this._tabBar.appendChild(btns);
       if (typeof safeCreateIcons === 'function') safeCreateIcons();
@@ -539,8 +539,23 @@ function createPaneTabManager(paneId) {
       menu.addEventListener('click', (e) => {
         const action = e.target.closest('.context-menu-item')?.dataset.action;
         if (action === 'moveTo') return; // handled by hover
-        if (action === 'splitRight') { if (pm) { pm.splitRight(); menu.remove(); return; } }
-        else if (action === 'splitDown') { if (pm) { pm.splitDown(); menu.remove(); return; } }
+        if (action === 'splitRight') {
+          if (pm && pm._hasAnyTab()) {
+            pm.splitRight();
+            // Transfer this specific tab to the new pane
+            const newPaneId = pm.panes.length - 1;
+            pm.transferTab(this.paneId, tabId, newPaneId);
+            menu.remove(); return;
+          }
+        }
+        else if (action === 'splitDown') {
+          if (pm && pm._hasAnyTab()) {
+            pm.splitDown();
+            const newPaneId = pm.panes.length - 1;
+            pm.transferTab(this.paneId, tabId, newPaneId);
+            menu.remove(); return;
+          }
+        }
         else if (action === 'closePane') { if (pm) { pm.closeActivePane(); menu.remove(); return; } }
         else if (action === 'close') this.close(tabId);
         else if (action === 'closeOthers') this.closeOthers(tabId);
@@ -660,20 +675,60 @@ const PaneManager = {
   // ------------------------------------------------------------------
   splitRight() {
     if (this.panes.length >= PANE_MAX) return;
+    // Don't split if no tab is open anywhere
+    if (!this._hasAnyTab()) return;
     this.layout = 'horizontal';
-    if (this.panes.length === 0) this._buildGrid(2);
-    else this._addPane();
+    if (this.panes.length === 0) {
+      this._buildGrid(2);
+      // Copy active tab to the new pane
+      this._copyActiveTabToNewPane();
+    } else {
+      this._addPane();
+    }
     this._persist();
   },
 
   splitDown() {
     if (this.panes.length >= PANE_MAX) return;
+    if (!this._hasAnyTab()) return;
     this.layout = 'vertical';
-    if (this.panes.length === 0) this._buildGrid(2);
-    else this._addPane();
+    if (this.panes.length === 0) {
+      this._buildGrid(2);
+      this._copyActiveTabToNewPane();
+    } else {
+      this._addPane();
+    }
     this._persist();
   },
 
+  /** Check if any pane has at least one tab */
+  _hasAnyTab() {
+    if (!this.isSplit()) {
+      // Check singleton in single-pane mode
+      if (window._singletonTabManager && window._singletonTabManager._tabs.length > 0)
+        return true;
+      return false;
+    }
+    for (const tm of Object.values(this.tabManagers)) {
+      if (tm._tabs && tm._tabs.length > 0) return true;
+    }
+    return false;
+  },
+
+  /** Copy the active tab to the newly created last pane */
+  _copyActiveTabToNewPane() {
+    const newPaneId = this.panes.length - 1;
+    const srcTm = this.tabManagers[this.activePaneId];
+    const dstTm = this.tabManagers[newPaneId];
+    if (!srcTm || !dstTm || !srcTm._activeTabId) return;
+    const cache = srcTm._tabCache[srcTm._activeTabId];
+    if (cache) {
+      setTimeout(() => {
+        dstTm.open(cache.vault, cache.path);
+      }, 150);
+    }
+  },
+
   // ------------------------------------------------------------------
   // Close pane
   // ------------------------------------------------------------------
@@ -1268,11 +1323,23 @@ if (typeof window !== 'undefined') {
     document.addEventListener('keydown', (e) => {
       if (e.ctrlKey && e.altKey && !e.shiftKey && e.key === '\\') {
         e.preventDefault();
-        PaneManager.splitRight();
+        if (PaneManager._hasAnyTab()) {
+          PaneManager.splitRight();
+          // Transfer active tab to new pane
+          const tm = PaneManager.getActiveTabManager();
+          if (tm && tm._activeTabId) {
+            setTimeout(() => {
+              const newPaneId = PaneManager.panes.length - 1;
+              PaneManager.transferTab(PaneManager.activePaneId === newPaneId ? 0 : PaneManager.activePaneId, tm._activeTabId, newPaneId);
+            }, 200);
+          }
+        }
       }
       if (e.ctrlKey && e.altKey && e.shiftKey && e.key === '\\') {
         e.preventDefault();
-        PaneManager.splitDown();
+        if (PaneManager._hasAnyTab()) {
+          PaneManager.splitDown();
+        }
       }
       // Close active pane
       if (e.ctrlKey && e.altKey && !e.shiftKey && (e.key === 'w' || e.key === 'W') && PaneManager.isSplit()) {

frontend/js/ui.js

@@ -2351,8 +2351,22 @@ export const TabManager = {
 
     menu.addEventListener("click", (e) => {
       const action = e.target.closest(".context-menu-item")?.dataset.action;
-      if (action === "splitRight") { if (window.PaneManager) { window.PaneManager.splitRight(); menu.remove(); return; } }
-      else if (action === "splitDown") { if (window.PaneManager) { window.PaneManager.splitDown(); menu.remove(); return; } }
+      if (action === "splitRight") {
+        if (window.PaneManager && window.PaneManager._hasAnyTab && window.PaneManager._hasAnyTab()) {
+          window.PaneManager.splitRight();
+          const newPaneId = window.PaneManager.panes.length - 1;
+          window.PaneManager.transferTab(0, tabId, newPaneId);
+          menu.remove(); return;
+        }
+      }
+      else if (action === "splitDown") {
+        if (window.PaneManager && window.PaneManager._hasAnyTab && window.PaneManager._hasAnyTab()) {
+          window.PaneManager.splitDown();
+          const newPaneId = window.PaneManager.panes.length - 1;
+          window.PaneManager.transferTab(0, tabId, newPaneId);
+          menu.remove(); return;
+        }
+      }
       else if (action === "closePane") { if (window.PaneManager) { window.PaneManager.closeActivePane(); menu.remove(); return; } }
       else if (action === "close") this.close(tabId);
       else if (action === "closeOthers") this.closeOthers(tabId);