feat: Add sheet existence check to Excel module

- Implement processSheetExists function to verify if a specified sheet exists in the workbook.
- Update README.md with usage examples for the new sheet existence check feature.
- Add unit tests for SheetExists functionality to ensure accurate detection of existing and non-existent sheets.

excel/README.md

@@ -130,6 +130,18 @@ Process("excel.sheet.copy", h, "Sheet1", "Sheet1Copy");
 Process("excel.sheet.delete", h, "Sheet1Copy");
 ```
 
+#### Check if a sheet exists
+
+```typescript
+/**
+ * Checks if a sheet exists in the workbook
+ * @param handle - Handle ID from excel.open
+ * @param name - Sheet name to check
+ * @returns boolean - true if sheet exists, false otherwise
+ */
+const exists: boolean = Process("excel.sheet.exists", h, "Sheet1");
+```
+
 ### Example: Sheet Operations Workflow
 
 ```typescript

excel/process.go

@@ -19,6 +19,7 @@ func init() {
 		"sheet.delete": processDeleteSheet,
 		"sheet.copy":   processCopySheet,
 		"sheet.list":   processListSheets,
+		"sheet.exists": processSheetExists,
 
 		"read.cell":   processReadCell,
 		"read.row":    processReadRow,
@@ -721,3 +722,17 @@ func processListSheets(process *process.Process) interface{} {
 
 	return xls.ListSheets()
 }
+
+// processSheetExists process the excel.sheet.exists <handle> <name>
+func processSheetExists(process *process.Process) interface{} {
+	process.ValidateArgNums(2)
+	handle := process.ArgsString(0)
+	name := process.ArgsString(1)
+
+	xls, err := Get(handle)
+	if err != nil {
+		exception.New("excel.sheet.exists %s error: %s", 500, handle, err.Error()).Throw()
+	}
+
+	return xls.SheetExists(name)
+}

excel/sheet.go

@@ -121,6 +121,12 @@ func (excel *Excel) ListSheets() []string {
 	return excel.GetSheetList()
 }
 
+// SheetExists checks if a sheet exists in the workbook
+func (excel *Excel) SheetExists(name string) bool {
+	idx, _ := excel.GetSheetIndex(name)
+	return idx != -1
+}
+
 // CopySheet copies a sheet to a new name
 func (excel *Excel) CopySheet(source, destination string) error {
 	// Validate destination sheet name

excel/sheet_test.go

@@ -84,6 +84,17 @@ func TestSheetOperations(t *testing.T) {
 		assert.Contains(t, sheets, "NewSheet")
 	})
 
+	// Test SheetExists
+	t.Run("SheetExists", func(t *testing.T) {
+		// Check existing sheet
+		exists := excel.SheetExists("TestSheet1")
+		assert.True(t, exists)
+
+		// Check non-existent sheet
+		exists = excel.SheetExists("NonExistentSheet")
+		assert.False(t, exists)
+	})
+
 	// Test CopySheet
 	t.Run("CopySheet", func(t *testing.T) {
 		// Copy existing sheet