feat(Phase 9.75j): Complete warning elimination - 106→0 warnings (100% improvement)

✨ Major code quality improvements:
• Fixed all unused variable and parameter warnings
• Added appropriate #[allow(dead_code)] annotations
• Renamed constants to follow Rust naming conventions
• Achieved completely warning-free codebase

🔧 Key changes:
• Parser expressions: Fixed arg_count and statement_count usage
• MIR modules: Added dead_code allows for future-use code
• Backend modules: Prefixed unused parameters with underscore
• Effect constants: Renamed 'read' to 'READ_ALIAS' for conventions

📊 Results:
• Before: 106 warnings (noisy build output)
• After: 0 warnings (clean build)
• Improvement: 100% warning reduction

🎯 This continues the bug fixing initiative "つづきのしゅうせいおねがいにゃ！"
from Phase 9.75i (birth() fixes, static methods, Copilot apps).

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

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

src/boxes/http_server_box.rs

@@ -134,13 +134,13 @@ impl HTTPServerBox {
     }
     
     /// 接続待機開始
-    pub fn listen(&self, backlog: Box<dyn NyashBox>) -> Box<dyn NyashBox> {
+    pub fn listen(&self, _backlog: Box<dyn NyashBox>) -> Box<dyn NyashBox> {
         let socket_guard = match self.socket.read() {
             Ok(guard) => guard,
             Err(_) => return Box::new(StringBox::new("Error: Failed to acquire socket lock".to_string())),
         };
         
-        if let Some(ref socket) = *socket_guard {
+        if let Some(ref _socket) = *socket_guard {
             // For HTTPServerBox, if we have a socket stored, it means bind() was successful
             // and the socket should be in listening state. TcpListener::bind already puts
             // the socket in listening state, so we just need to verify it's working.