fix(data-grid): exclude non-navigable columns from copy operation

When copying cells after selecting rows via checkbox, the copy operation was including the "select" column (and other non-navigable columns) in the TSV output. This caused an empty leading column in the clipboard data, which then shifted all pasted values by one column when pasting.

The fix:
1. Skips non-navigable columns (select, actions) during iteration in serializeCellsToTsv
2. Builds a navigableCells array as we iterate (more efficient than filtering afterward)
3. Returns navigableCells for accurate cell counts in toast messages and cutCells state

Co-authored-by: Cursor <cursoragent@cursor.com>

Author: sadmann7

src/hooks/use-data-grid.ts

@@ -560,9 +560,18 @@ function useDataGrid<TData>({
       number,
       Map<string, ReturnType<Row<TData>["getVisibleCells"]>[number]>
     >();
+    const navigableCells: string[] = [];
 
     for (const cellKey of selectedCellsArray) {
       const { rowIndex, columnId } = parseCellKey(cellKey);
+      
+      // Skip non-navigable columns (like "select", "actions")
+      if (columnId && NON_NAVIGABLE_COLUMN_IDS.has(columnId)) {
+        continue;
+      }
+      
+      // Track navigable cells for accurate counts
+      navigableCells.push(cellKey);
 
       if (columnId && !seenColumnIds.has(columnId)) {
         seenColumnIds.add(columnId);
@@ -598,7 +607,7 @@ function useDataGrid<TData>({
     }
 
     const colIndices = new Set<number>();
-    for (const cellKey of selectedCellsArray) {
+    for (const cellKey of navigableCells) {
       const { columnId } = parseCellKey(cellKey);
       const colIndex = selectedColumnIds.indexOf(columnId);
       if (colIndex >= 0) {
@@ -621,7 +630,7 @@ function useDataGrid<TData>({
       )
       .join("\n");
 
-    return { tsvData, selectedCellsArray };
+    return { tsvData, selectedCellsArray: navigableCells };
   }, [store]);
 
   const onCellsCopy = React.useCallback(async () => {