fix(jit): NewBoxのJIT安全化とDebugBox Phase 1実装

- NewBoxのJIT扱いを安全化（src/jit/lower/core.rs）
  - NYASH_USE_PLUGIN_BUILTINS=1 && args.is_empty() かつ StringBox/IntegerBox のみJIT許可
  - ArrayBox/MapBox等のプラグインBoxまたは引数ありはunsupportedとしてカウント
  - unsupported>0の関数はJIT対象外となりVM実行にフォールバック（Segfault回避）

- DebugBox Phase 1実装（JITトレース機能）
  - tracePluginCalls(bool)でJITシムトレースON/OFF
  - getJitEvents()で直近のJITイベント取得
  - src/jit/shim_trace.rs追加でトレース基盤実装

- Printのサポート
  - PrintはJIT非対応に戻しVM経路で確実に出力（出力消失解消）

- テストとサンプル追加
  - examples/jit_plugin_invoke_param_array.nyash: 最小JITスモークテスト
  - examples/py_result_*.nyash: Python plugin結果チェーン処理デモ

- PyRuntimeBox拡張
  - str()メソッドでPyObjectのstring表現を取得可能に
  - エラーハンドリング改善とResultチェーンサポート

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

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

examples/jit_plugin_invoke_param_array.nyash

@@ -0,0 +1,27 @@
+// JIT plugin_invoke smoke: no NewBox in JITed function
+// Requires: array plugin built + nyash.toml configured
+// Build plugins:
+//   (cd plugins/nyash-array-plugin && cargo build --release)
+// Run (JIT helper only):
+//   NYASH_USE_PLUGIN_BUILTINS=1 NYASH_JIT_EXEC=1 NYASH_JIT_THRESHOLD=1 \
+//   NYASH_JIT_SHIM_TRACE=1 NYASH_CLI_VERBOSE=1 \
+//   ./target/release/nyash --backend vm examples/jit_plugin_invoke_param_array.nyash
+
+static box Main {
+  main() {
+    local a
+    // Create ArrayBox in VM (this function stays in VM)
+    a = new ArrayBox()
+    a.push(1)
+    a.push(2)
+    a.push(3)
+    // Call helper (this function should JIT) — only BoxCall on parameter
+    return me.helper(a)
+  }
+
+  helper(arr) {
+    // No allocations/new here; only plugin call on parameter
+    return arr.length()
+  }
+}
+

examples/py_eval_autodecode_demo.nyash

@@ -0,0 +1,16 @@
+// Auto-decode demo for eval/getattr/call
+// Run:
+//   NYASH_PY_AUTODECODE=1 NYASH_CLI_VERBOSE=1 ./target/release/nyash --backend vm examples/py_eval_autodecode_demo.nyash
+
+static box Main {
+  main() {
+    local py, n, s
+    py = new PyRuntimeBox()
+    n = py.eval("3.14159")
+    s = py.eval("'hello world'")
+    me.console.log("eval num=", n.toString())
+    me.console.log("eval str=", s)
+    return 0
+  }
+}
+

examples/py_result_chain_complete.nyash

@@ -0,0 +1,45 @@
+// Complete Result chain test (importR → getattrR → callR)
+static box Main {
+  main() {
+    local py = new PyRuntimeBox()
+    
+    // Success chain: math.sqrt(25) 
+    print("=== Success chain test ===")
+    local mathR = py.importR("math")
+    print("1. importR('math') = " + mathR)
+    
+    if mathR.isOk() {
+      local math = mathR.unwrap()
+      local sqrtR = math.getattrR("sqrt")
+      print("2. getattrR('sqrt') = " + sqrtR)
+      
+      if sqrtR.isOk() {
+        local sqrt = sqrtR.unwrap()
+        local resultR = sqrt.callR(25)
+        print("3. callR(25) = " + resultR)
+        
+        if resultR.isOk() {
+          local result = resultR.unwrap()
+          print("4. Final value = " + result.str())
+        }
+      }
+    }
+    
+    // Error chain: test error handling
+    print("\n=== Error chain test ===")
+    local badModR = py.importR("nonexistent_module")
+    print("importR('nonexistent_module') = " + badModR)
+    
+    // Test getattrR error
+    local mathNormal = py.import("math")
+    local badAttrR = mathNormal.getattrR("nonexistent_attr")
+    print("getattrR('nonexistent_attr') = " + badAttrR)
+    
+    // Test callR with invalid args
+    local sqrtNormal = mathNormal.getattr("sqrt")
+    local badCallR = sqrtNormal.callR("invalid_arg")
+    print("callR('invalid_arg') = " + badCallR)
+    
+    return 0
+  }
+}

examples/py_result_chain_demo.nyash

@@ -0,0 +1,21 @@
+// Result-returning variants demo (R methods)
+// Run:
+//   NYASH_CLI_VERBOSE=1 ./target/release/nyash --backend vm examples/py_result_chain_demo.nyash
+
+static box Main {
+  main() {
+    local py, mR, fR, rR, badR
+    py = new PyRuntimeBox()
+    // Use R variants to get Result boxes
+    mR = py.importR("math")
+    fR = mR.getattrR("sqrt")
+    rR = fR.callR(9)
+    me.console.log("sqrt(9) via R=", rR.toString())
+
+    // Error example: getattrR on missing name
+    badR = mR.getattrR("no_such_attr")
+    me.console.log("missing getattrR=", badR.toString())
+    return 0
+  }
+}
+

examples/py_result_chain_demo_fixed.nyash

@@ -0,0 +1,34 @@
+// Result-returning variants demo (R methods)
+// Run:
+//   NYASH_CLI_VERBOSE=1 ./target/release/nyash --backend vm examples/py_result_chain_demo_fixed.nyash
+
+static box Main {
+  init { console }
+  
+  main() {
+    me.console = new ConsoleBox()
+    
+    local py, mR, fR, rR, badR
+    py = new PyRuntimeBox()
+    
+    // Use R variants to get Result boxes
+    me.console.log("Testing importR...")
+    mR = py.importR("math")
+    me.console.log("importR result=", mR.toString())
+    
+    me.console.log("Testing getattrR on sqrt...")
+    fR = mR.getattrR("sqrt")
+    me.console.log("getattrR result=", fR.toString())
+    
+    me.console.log("Testing callR with 9...")
+    rR = fR.callR(9)
+    me.console.log("callR result=", rR.toString())
+    
+    // Error example: getattrR on missing attribute
+    me.console.log("Testing error case...")
+    badR = mR.getattrR("no_such_attr")
+    me.console.log("missing getattrR=", badR.toString())
+    
+    return 0
+  }
+}

examples/py_result_simple_test.nyash

@@ -0,0 +1,25 @@
+// Simple test for Result-returning Python APIs
+static box Main {
+  main() {
+    local py = new PyRuntimeBox()
+    
+    // Test importR (Result variant)
+    print("Testing importR...")
+    local mathR = py.importR("math")
+    print("importR returned: " + mathR)
+    
+    // Test error case
+    print("Testing import error...")
+    local badR = py.importR("no_such_module_xxxxx")
+    print("importR error returned: " + badR)
+    
+    // Normal import for comparison
+    print("Testing normal import...")
+    local math = py.import("math")
+    local sqrt = math.getattr("sqrt")
+    local result = sqrt.call(16)
+    print("sqrt(16) = " + result.str())
+    
+    return 0
+  }
+}