feat: Add grammar fetch and comparison tooling

- Add fetch_bind_grammar.py for MCP-based grammar file retrieval
- Add compare_bind_versions.py for version differences analysis
- Add process_mcp_result.py for handling base64-encoded MCP output
- Create upstream directory structure with fetching instructions
- Document grammar file locations and structure

scripts/save_grammar_file.py

@@ -0,0 +1,37 @@
+#!/usr/bin/env python3
+"""Helper script to save base64-encoded grammar file from MCP tool output."""
+
+import base64
+import json
+import sys
+from pathlib import Path
+
+def main():
+    if len(sys.argv) != 3:
+        print("Usage: save_grammar_file.py <json_file> <output_path>")
+        sys.exit(1)
+    
+    json_file = Path(sys.argv[1])
+    output_path = Path(sys.argv[2])
+    
+    # Read JSON from MCP tool output
+    with open(json_file, 'r') as f:
+        data = json.load(f)
+    
+    # Extract and decode base64 content
+    if 'Result' in data and 'content' in data['Result']:
+        content_b64 = data['Result']['content']
+        content = base64.b64decode(content_b64).decode('utf-8')
+        
+        # Save to output path
+        output_path.parent.mkdir(parents=True, exist_ok=True)
+        with open(output_path, 'w', encoding='utf-8') as f:
+            f.write(content)
+        
+        print(f"✓ Saved: {output_path}")
+    else:
+        print(f"✗ Error: No content found in JSON", file=sys.stderr)
+        sys.exit(1)
+
+if __name__ == "__main__":
+    main()