feat: finalisation split view #75 — boutons, nav clavier, palette, ROADMAP

Ajouts:
- C3: Boutons Split ⊞→ ⊞↓ dans la barre d'onglets (visibles au survol)
- C2: Ctrl+Alt+←/→/↑/↓ navigation entre panneaux
- C2: Ctrl+Shift+Alt+W fermer tous les autres panneaux
- H1: 5 commandes palette (Split R/D, Close Pane, Focus Next/Prev)
- ROADMAP.md: section 75 mise à jour avec statut 80% complété

CSS: .tab-split-buttons, .tab-split-btn avec opacity hover

frontend/js/pane-manager.js

@@ -46,6 +46,37 @@ function createPaneTabManager(paneId) {
         this._tabList = document.getElementById('tab-list-' + paneId);
       if (!this._contentArea)
         this._contentArea = document.getElementById('content-area-' + paneId);
+
+      // Add split buttons to the tab bar (right side)
+      this._ensureSplitButtons();
+    },
+
+    _ensureSplitButtons() {
+      if (!this._tabBar) return;
+      // Remove existing split buttons if any
+      const existing = this._tabBar.querySelector('.tab-split-buttons');
+      if (existing) existing.remove();
+
+      const btns = document.createElement('div');
+      btns.className = 'tab-split-buttons';
+      btns.innerHTML = `
+        <button class="tab-split-btn" title="Diviser à droite (Ctrl+Alt+\\)" data-action="split-right">
+          <i data-lucide="panel-right" style="width:13px;height:13px"></i>
+        </button>
+        <button class="tab-split-btn" title="Diviser en bas (Ctrl+Alt+Shift+\\)" data-action="split-down">
+          <i data-lucide="panel-bottom" style="width:13px;height:13px"></i>
+        </button>
+      `;
+      btns.querySelector('[data-action="split-right"]').addEventListener('click', (e) => {
+        e.stopPropagation();
+        if (window.PaneManager) window.PaneManager.splitRight();
+      });
+      btns.querySelector('[data-action="split-down"]').addEventListener('click', (e) => {
+        e.stopPropagation();
+        if (window.PaneManager) window.PaneManager.splitDown();
+      });
+      this._tabBar.appendChild(btns);
+      if (typeof safeCreateIcons === 'function') safeCreateIcons();
     },
 
     getContentArea() {
@@ -1063,10 +1094,36 @@ if (typeof window !== 'undefined') {
         e.preventDefault();
         PaneManager.splitDown();
       }
+      // Close active pane
       if (e.ctrlKey && e.altKey && !e.shiftKey && (e.key === 'w' || e.key === 'W') && PaneManager.isSplit()) {
         e.preventDefault();
         PaneManager.closeActivePane();
       }
+      // Close all other panes
+      if (e.ctrlKey && e.shiftKey && e.altKey && (e.key === 'w' || e.key === 'W') && PaneManager.isSplit()) {
+        e.preventDefault();
+        PaneManager.closeOtherPanes();
+      }
+      // Navigate between panes
+      if (e.ctrlKey && e.altKey && PaneManager.isSplit()) {
+        if (e.key === 'ArrowRight') {
+          e.preventDefault();
+          const next = (PaneManager.activePaneId + 1) % PaneManager.panes.length;
+          PaneManager.setActivePane(next);
+        } else if (e.key === 'ArrowLeft') {
+          e.preventDefault();
+          const prev = (PaneManager.activePaneId - 1 + PaneManager.panes.length) % PaneManager.panes.length;
+          PaneManager.setActivePane(prev);
+        } else if (e.key === 'ArrowDown' && PaneManager.layout === 'vertical') {
+          e.preventDefault();
+          const next = (PaneManager.activePaneId + 1) % PaneManager.panes.length;
+          PaneManager.setActivePane(next);
+        } else if (e.key === 'ArrowUp' && PaneManager.layout === 'vertical') {
+          e.preventDefault();
+          const prev = (PaneManager.activePaneId - 1 + PaneManager.panes.length) % PaneManager.panes.length;
+          PaneManager.setActivePane(prev);
+        }
+      }
     });
     // Init — wait for DOM + singleton TabManager to be ready
     setTimeout(() => {