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/llvm.rs

@@ -12,6 +12,13 @@ impl NyashRunner {
         // Initialize plugin host so method_id injection can resolve plugin calls
         crate::runner_plugin_init::init_bid_plugins();
 
+        // Friendly plugin guard (non‑strict): unify diagnostics across modes
+        crate::runner::modes::common_util::plugin_guard::check_and_report(
+            false,
+            crate::config::env::env_bool("NYASH_JSON_ONLY"),
+            "llvm",
+        );
+
         // Read the file
         let code = match fs::read_to_string(filename) {
             Ok(content) => content,