MAESTRO: Add handleUnifiedTabReorder function for unified tab reordering

Implements unified tab reorder functionality that operates on the
unifiedTabOrder array, allowing both AI and file preview tabs to be
reordered relative to each other. This supplements the existing
handleTabReorder (AI-only) for the unified tab system.

Changes:
- Added handleUnifiedTabReorder in App.tsx with index validation
- Propagated through useMainPanelProps.ts, MainPanel.tsx, TabBar.tsx

src/renderer/App.tsx

@@ -5300,6 +5300,40 @@ You are taking over this conversation. Based on the context above, provide a bri
 		);
 	}, []);
 
+	/**
+	 * Reorder tabs in the unified tab order. This allows moving both AI and file tabs
+	 * relative to each other. The fromIndex and toIndex refer to positions in unifiedTabOrder.
+	 * This replaces/supplements handleTabReorder for the unified tab system.
+	 */
+	const handleUnifiedTabReorder = useCallback(
+		(fromIndex: number, toIndex: number) => {
+			setSessions((prev) =>
+				prev.map((s) => {
+					if (s.id !== activeSessionIdRef.current) return s;
+
+					// Validate indices
+					if (
+						fromIndex < 0 ||
+						fromIndex >= s.unifiedTabOrder.length ||
+						toIndex < 0 ||
+						toIndex >= s.unifiedTabOrder.length ||
+						fromIndex === toIndex
+					) {
+						return s;
+					}
+
+					// Reorder the unifiedTabOrder array
+					const newOrder = [...s.unifiedTabOrder];
+					const [movedRef] = newOrder.splice(fromIndex, 1);
+					newOrder.splice(toIndex, 0, movedRef);
+
+					return { ...s, unifiedTabOrder: newOrder };
+				})
+			);
+		},
+		[]
+	);
+
 	/**
 	 * Internal tab close handler that performs the actual close.
 	 * Wizard tabs are closed without being added to history (they can't be restored).
@@ -12588,6 +12622,7 @@ You are taking over this conversation. Based on the context above, provide a bri
 		handleNewTab,
 		handleRequestTabRename,
 		handleTabReorder,
+		handleUnifiedTabReorder,
 		handleUpdateTabByClaudeSessionId,
 		handleTabStar,
 		handleTabMarkUnread,