fix(advanced_table): Init row_edit_buffer on Ctrl+N insert

Start edit buffer for new row immediately after Ctrl+N insertion,
enabling Excel-style editing from the first keystroke.

src/widgets/advanced_table/advanced_table.zig

@@ -807,6 +807,8 @@ fn handleKeyboard(
                 0;
             if (table_state.insertRow(insert_idx)) |new_idx| {
                 table_state.selectCell(new_idx, 0);
+                // Inicializar buffer de edición para la nueva fila (Excel-style)
+                table_state.row_edit_buffer.startEdit(table_core.NEW_ROW_ID, new_idx, true);
                 result.row_inserted = true;
                 result.selection_changed = true;
             } else |_| {}