feat: add advanced dependency resolution and package download tools

- Add DependencyParser for parsing and categorizing package dependencies
- Add DependencyResolver for recursive dependency tree analysis
- Add PackageDownloader for downloading packages with dependencies
- Add resolve_dependencies MCP tool for comprehensive dependency analysis
- Add download_package MCP tool for package collection
- Support Python version filtering and extra dependencies
- Include comprehensive test coverage for new functionality
- Add demonstration script for new features
- Update README with new capabilities and usage examples

Signed-off-by: Hal <hal.long@outlook.com>

examples/dependency_analysis_demo.py

@@ -0,0 +1,157 @@
+#!/usr/bin/env python3
+"""
+Demonstration of PyPI Query MCP Server dependency analysis and download features.
+
+This script shows how to use the new dependency resolution and package download
+capabilities for analyzing Python packages like PySide2.
+"""
+
+import asyncio
+import json
+from pathlib import Path
+
+from pypi_query_mcp.tools.dependency_resolver import resolve_package_dependencies
+from pypi_query_mcp.tools.package_downloader import download_package_with_dependencies
+
+
+async def analyze_pyside2_dependencies():
+    """Analyze PySide2 dependencies for Python 3.10."""
+    print("🔍 Analyzing PySide2 dependencies for Python 3.10...")
+    
+    try:
+        result = await resolve_package_dependencies(
+            package_name="PySide2",
+            python_version="3.10",
+            include_extras=[],
+            include_dev=False,
+            max_depth=3
+        )
+        
+        print(f"✅ Successfully resolved dependencies for {result['package_name']}")
+        print(f"📊 Summary:")
+        summary = result['summary']
+        print(f"   - Total packages: {summary['total_packages']}")
+        print(f"   - Runtime dependencies: {summary['total_runtime_dependencies']}")
+        print(f"   - Max depth: {summary['max_depth']}")
+        
+        print(f"\n📦 Package list:")
+        for i, pkg in enumerate(summary['package_list'][:10], 1):  # Show first 10
+            print(f"   {i}. {pkg}")
+        
+        if len(summary['package_list']) > 10:
+            print(f"   ... and {len(summary['package_list']) - 10} more packages")
+        
+        return result
+        
+    except Exception as e:
+        print(f"❌ Error analyzing dependencies: {e}")
+        return None
+
+
+async def download_pyside2_packages():
+    """Download PySide2 and its dependencies."""
+    print("\n📥 Downloading PySide2 and dependencies...")
+    
+    download_dir = Path("./pyside2_downloads")
+    
+    try:
+        result = await download_package_with_dependencies(
+            package_name="PySide2",
+            download_dir=str(download_dir),
+            python_version="3.10",
+            include_extras=[],
+            include_dev=False,
+            prefer_wheel=True,
+            verify_checksums=True,
+            max_depth=2  # Limit depth for demo
+        )
+        
+        print(f"✅ Download completed!")
+        print(f"📊 Download Summary:")
+        summary = result['summary']
+        print(f"   - Total packages: {summary['total_packages']}")
+        print(f"   - Successful downloads: {summary['successful_downloads']}")
+        print(f"   - Failed downloads: {summary['failed_downloads']}")
+        print(f"   - Total size: {summary['total_downloaded_size']:,} bytes")
+        print(f"   - Success rate: {summary['success_rate']:.1f}%")
+        print(f"   - Download directory: {summary['download_directory']}")
+        
+        if result['failed_downloads']:
+            print(f"\n⚠️  Failed downloads:")
+            for failure in result['failed_downloads']:
+                print(f"   - {failure['package']}: {failure['error']}")
+        
+        return result
+        
+    except Exception as e:
+        print(f"❌ Error downloading packages: {e}")
+        return None
+
+
+async def analyze_small_package():
+    """Analyze a smaller package for demonstration."""
+    print("\n🔍 Analyzing 'click' package dependencies...")
+    
+    try:
+        result = await resolve_package_dependencies(
+            package_name="click",
+            python_version="3.10",
+            include_extras=[],
+            include_dev=False,
+            max_depth=5
+        )
+        
+        print(f"✅ Successfully resolved dependencies for {result['package_name']}")
+        
+        # Show detailed dependency tree
+        print(f"\n🌳 Dependency Tree:")
+        dependency_tree = result['dependency_tree']
+        
+        for pkg_name, pkg_info in dependency_tree.items():
+            indent = "  " * pkg_info['depth']
+            print(f"{indent}- {pkg_info['name']} ({pkg_info['version']})")
+            
+            runtime_deps = pkg_info['dependencies']['runtime']
+            if runtime_deps:
+                for dep in runtime_deps[:3]:  # Show first 3 dependencies
+                    print(f"{indent}  └─ {dep}")
+                if len(runtime_deps) > 3:
+                    print(f"{indent}  └─ ... and {len(runtime_deps) - 3} more")
+        
+        return result
+        
+    except Exception as e:
+        print(f"❌ Error analyzing dependencies: {e}")
+        return None
+
+
+async def main():
+    """Main demonstration function."""
+    print("🚀 PyPI Query MCP Server - Dependency Analysis Demo")
+    print("=" * 60)
+    
+    # Analyze a small package first
+    click_result = await analyze_small_package()
+    
+    # Analyze PySide2 dependencies
+    pyside2_result = await analyze_pyside2_dependencies()
+    
+    # Optionally download packages (commented out to avoid large downloads in demo)
+    # download_result = await download_pyside2_packages()
+    
+    print("\n" + "=" * 60)
+    print("✨ Demo completed!")
+    
+    if click_result:
+        print(f"📝 Click analysis saved to: click_dependencies.json")
+        with open("click_dependencies.json", "w") as f:
+            json.dump(click_result, f, indent=2)
+    
+    if pyside2_result:
+        print(f"📝 PySide2 analysis saved to: pyside2_dependencies.json")
+        with open("pyside2_dependencies.json", "w") as f:
+            json.dump(pyside2_result, f, indent=2)
+
+
+if __name__ == "__main__":
+    asyncio.run(main())