🚨 Critical Issue #76: SocketBox Method Call Deadlock Investigation

## 🎯 Problem Identification Complete
- SocketBox method calls (bind, isServer, toString) cause infinite blocking
- Root cause: Method resolution pipeline deadlock before execute_socket_method
- Other Box types (ArrayBox, StringBox, MapBox) work normally
- Arc<Mutex> reference sharing confirmed working (Arc addresses match = true)

## 🔧 Debug Infrastructure Added
- Comprehensive debug logging in socket_box.rs (bind, isServer, clone, toString)
- Method call tracing in http_methods.rs
- Deadlock detection points identified at interpreter expressions.rs:462-464

## 📋 Issue #76 Created for Copilot Investigation
- Systematic root cause analysis requirements (Architecture→Parser→Runtime levels)
- Comprehensive test cases: minimal/comprehensive/comparison scenarios
- Strict prohibition of band-aid fixes - architectural analysis required
- Hypothesis: Multiple Arc<Mutex> combinations causing circular deadlock

## 🧪 Test Suite Added
- test_socket_deadlock_minimal.nyash: Minimal reproduction case
- test_socket_methods_comprehensive.nyash: All methods deadlock verification
- test_other_boxes_working.nyash: Normal Box operation confirmation
- SOCKETBOX_ISSUE_REPRODUCTION.md: Complete reproduction guide

## 📊 Impact Assessment
- Phase 9 HTTP server implementation completely blocked
- SocketBox functionality entirely non-functional
- Critical blocker for production readiness
- Requires immediate systematic investigation

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

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

src/interpreter/core.rs

@@ -669,7 +669,7 @@ impl NyashInterpreter {
             };
             
             // 🌍 this変数をバインドしてstatic初期化実行（me構文のため）
-            self.declare_local_variable("me", static_instance);
+            self.declare_local_variable("me", (*static_instance).clone_box());
             
             for stmt in init_statements {
                 self.execute_statement(stmt)?;
@@ -722,7 +722,7 @@ impl NyashInterpreter {
         // GlobalBoxのfieldsに直接挿入
         {
             let mut fields = global_box.fields.lock().unwrap();
-            fields.insert("statics".to_string(), Box::new(statics_box));
+            fields.insert("statics".to_string(), Arc::new(statics_box));
         }
             
         eprintln!("🌍 statics namespace created in GlobalBox successfully");
@@ -751,7 +751,7 @@ impl NyashInterpreter {
         // statics InstanceBoxのfieldsに直接挿入（動的フィールド追加）
         {
             let mut fields = statics_instance.fields.lock().unwrap();
-            fields.insert(name.to_string(), Box::new(instance));
+            fields.insert(name.to_string(), Arc::new(instance));
         }
         
         eprintln!("🔥 Static box '{}' instance registered in statics namespace", name);