Phase 21.3 WIP: Hako Source Checker improvements - HC011/HC016/HC017 実装完了

主な変更:
- ✅ HC011 (dead methods) 実装・テスト緑
- ✅ HC016 (unused alias) 実装・テスト緑
- ✅ HC017 (non-ascii quotes) 実装完了
- 🔧 tokenizer/parser_core 強化（AST優先ルート）
- 🛡️ plugin_guard.rs 追加（stderr専用出力）
- 📋 テストインフラ整備（run_tests.sh改善）

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

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

src/runner/modes/vm.rs

@@ -67,30 +67,13 @@ impl NyashRunner {
             }
             std::env::set_var("NYASH_PLUGIN_OVERRIDE_TYPES", override_types.join(","));
 
-            // Strict mode: verify providers exist for override types
-            if crate::config::env::env_bool("NYASH_VM_PLUGIN_STRICT") {
-                let v2 = nyash_rust::runtime::get_global_registry();
-                let mut missing: Vec<String> = Vec::new();
-                for t in [
-                    "FileBox",
-                    "ConsoleBox",
-                    "ArrayBox",
-                    "MapBox",
-                    "StringBox",
-                    "IntegerBox",
-                ] {
-                    if v2.get_provider(t).is_none() {
-                        missing.push(t.to_string());
-                    }
-                }
-                if !missing.is_empty() {
-                    eprintln!(
-                        "❌ VM plugin-first strict: missing providers for: {:?}",
-                        missing
-                    );
-                    std::process::exit(1);
-                }
-            }
+            // Centralized plugin guard
+            let strict = crate::config::env::env_bool("NYASH_VM_PLUGIN_STRICT");
+            crate::runner::modes::common_util::plugin_guard::check_and_report(
+                strict,
+                quiet_pipe,
+                "vm",
+            );
         }
 
         // Read the file