feat(benchmark): add comprehensive performance benchmarking system

🚀 Phase 8.2 PoC2 Achievement: 280x WASM performance boost proven\!

## New Features:
- Complete benchmark framework (src/benchmarks.rs)
- CLI integration: --benchmark --iterations options
- 3-backend comparison: Interpreter/VM/WASM
- Automated performance measurement & reporting

## Benchmark Results (100 iterations average):
- WASM: 0.17ms (280x faster than Interpreter\!)
- VM: 16.97ms (2.9x faster than Interpreter)
- Interpreter: 48.59ms (baseline)

## Added Files:
- benchmarks/bench_{light,medium,heavy}.nyash - Test cases
- benchmark_summary_20250814.md - Clean results
- wasm_demo/ - Browser execution environment

## Documentation Updates:
- docs/execution-backends.md - Added benchmark usage
- docs/CURRENT_TASK.md - Phase 8.3 Copilot coordination
- CLAUDE.md - Quick benchmark access

## Copilot Integration Ready:
- Phase 8.3 merge conflict avoidance strategy documented
- Benchmark framework ready for Box operation performance validation
- CLI integration preserved for future enhancements

🤖 Generated with [Claude Code](https://claude.ai/code)

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

wasm_demo/server.py

@@ -0,0 +1,46 @@
+#!/usr/bin/env python3
+"""
+Simple HTTP server for WASM demo
+Serves with proper MIME types for WASM files
+"""
+
+import http.server
+import socketserver
+import os
+
+class WASMHTTPRequestHandler(http.server.SimpleHTTPRequestHandler):
+    def end_headers(self):
+        # Add CORS headers
+        self.send_header('Access-Control-Allow-Origin', '*')
+        self.send_header('Access-Control-Allow-Methods', 'GET, POST, OPTIONS')
+        self.send_header('Access-Control-Allow-Headers', 'Content-Type')
+        super().end_headers()
+    
+    def guess_type(self, path):
+        result = super().guess_type(path)
+        mimetype = result[0] if result else 'text/plain'
+        
+        # Set proper MIME types
+        if path.endswith('.wasm'):
+            mimetype = 'application/wasm'
+        elif path.endswith('.wat'):
+            mimetype = 'text/plain'
+            
+        return mimetype
+
+PORT = 8000
+DIRECTORY = os.path.dirname(os.path.abspath(__file__))
+
+os.chdir(DIRECTORY)
+
+with socketserver.TCPServer(("", PORT), WASMHTTPRequestHandler) as httpd:
+    print(f"🚀 Nyash WASM Demo Server")
+    print(f"📦 Serving at http://localhost:{PORT}")
+    print(f"📂 Directory: {DIRECTORY}")
+    print(f"\n✨ Open http://localhost:{PORT}/index.html in your browser!")
+    print(f"Press Ctrl-C to stop the server...")
+    
+    try:
+        httpd.serve_forever()
+    except KeyboardInterrupt:
+        print("\n👋 Server stopped.")