fix: Add --rules parameter and improve validate command

- Add --rules parameter to support validation rule shorthand format
- Add --rules-file parameter to load rules from JSON file
- Add --output parameter to write validation report to file
- Implement email pattern validation for 'email:email' rules
- Implement wildcard '*' rule to validate all columns
- Show type mismatches as warnings instead of errors
- Fix exit code logic to only fail on critical errors
- Handle empty files gracefully
- Add comprehensive report structure with file metadata

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: codewizdave

excel_toolkit/commands/head.py

@@ -41,8 +41,15 @@ def head(
         format: Output format: table, csv, or json
 
     Raises:
-        typer.Exit: If file cannot be read
+        typer.Exit: If file cannot be read or invalid format
     """
+    # 0. Validate format
+    valid_formats = ["table", "csv", "json"]
+    if format not in valid_formats:
+        typer.echo(f"Unknown format: {format}", err=True)
+        typer.echo(f"Supported formats: {', '.join(valid_formats)}", err=True)
+        raise typer.Exit(1)
+
     # 1. Read file
     df = read_data_file(file_path, sheet)
 
@@ -60,7 +67,7 @@ def head(
 
     # 5. Display file info
     path = Path(file_path)
-    format_file_info(path, len(df), len(df.columns))
+    typer.echo(format_file_info(str(path), sheet=sheet, total_rows=len(df), total_cols=len(df.columns)))
 
     # 6. Show column information if requested
     if show_columns: