feat: split view pro — TabManager indépendant par panneau avec drag & drop cross-pane

- PaneTabManager factory: chaque panneau a sa propre instance avec ses propres onglets
- Drag & drop d'onglets entre panneaux (application/obsigate-tab dataTransfer)
- Split copie l'onglet actif dans le nouveau panneau
- TabManager singleton: délégation automatique vers le panneau actif en mode split
- Persistance complète par panneau (tabs, activeTab, previewTab)
- viewer.js: getContentArea() priorise window._activePaneContentArea
- 307 tests verts, déployé sur 192.168.30.101:2020

tests/test_pane_manager.py

@@ -76,14 +76,16 @@ class TestPaneManagerStaticAssets:
         # Only the fallback inside getContentArea should remain
         assert len(direct_refs) <= 2, f"Too many direct content-area refs: {direct_refs}"
 
-    def test_ui_tab_manager_has_pane_helpers(self):
-        """TabManager in ui.js has _getContentArea, _getTabBar, _getTabList."""
+    def test_ui_tab_manager_has_delegation(self):
+        """TabManager in ui.js delegates to getActiveTabManager() when split."""
         path = PROJECT_ROOT / "frontend" / "js" / "ui.js"
         content = path.read_text()
-        assert "_getContentArea()" in content
-        assert "_getTabBar()" in content
-        assert "_getTabList()" in content
-        assert "activatePaneTab(" in content
+        assert "getActiveTabManager" in content
+        assert "PaneManager.isSplit()" in content
+        # Must have delegation in entry-point methods
+        assert "window.getActiveTabManager().openPreview" in content
+        assert "window.getActiveTabManager().openPersistent" in content
+        assert "window.getActiveTabManager().close(" in content
 
     def test_ui_context_menu_has_split_actions(self):
         """Tab context menu includes 'Diviser à droite' and 'Diviser en bas'."""