Phase 12: VM/JIT identical execution tests + host API slot routing

ChatGPT5による統一実行パス実装：
- VM/JIT同一実行テスト追加（Array/Map/String/Instance）
- host_api slot経由呼び出し（NYASH_JIT_HOST_BRIDGE=1）
- extern_registry拡張（console系メソッドslot登録）
- CI: vm-jit-identical.yml（STRICT/非STRICT両系テスト）
- InstanceBox getField/setField slot 1,2統一

技術的改善：
- JIT: ops_ext委譲による統一メソッド解決
- VM: vtable/PIC/名前ベースフォールバック階層
- host_bridge: TLV encode/decode BoxRef対応
- C ABI: nyrt_host_api.h外部公開ヘッダー

テスト追加：
- identical_exec_collections: Array/Map操作一致
- identical_exec_instance: ユーザー定義Box一致
- identical_exec_string: StringBox操作一致
- host_reverse_slot: 逆引きslot解決テスト

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

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

include/nyrt_host_api.h

@@ -0,0 +1,47 @@
+// NyRT Host Reverse-Call C ABI (Phase 12)
+// Minimal header for plugins → host calls using TLV-encoded arguments.
+//
+// Exports:
+//  - nyrt_host_call_name: call method by name
+//  - nyrt_host_call_slot: call by numeric slot (stable ABI)
+//
+// TLV Tags (subset):
+//  tag=1  -> bool (1 byte)
+//  tag=2  -> i32  (4 bytes, LE)
+//  tag=3  -> i64/u64 (8 bytes, LE)
+//  tag=5  -> f64 (8 bytes, LE)
+//  tag=6/7-> string (utf8)
+//  tag=8  -> PluginHandle (type_id:u32, instance_id:u32)
+//  tag=9  -> HostHandle (u64) for user/builtin boxes
+//
+// Slots (subset):
+//  InstanceBox: 1(getField), 2(setField), 3(has), 4(size)
+//  ArrayBox:    100(get), 101(set), 102(len)
+//  MapBox:      200(size), 201(len), 202(has), 203(get), 204(set)
+//  StringBox:   300(len)
+
+#pragma once
+#include <stdint.h>
+#include <stddef.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+// Call a method by name on a HostHandle receiver.
+// Arguments are TLV-encoded values; output is a single TLV value.
+// Returns 0 on success.
+int32_t nyrt_host_call_name(uint64_t handle,
+                            const uint8_t* method_ptr, size_t method_len,
+                            const uint8_t* args_ptr, size_t args_len,
+                            uint8_t* out_ptr, size_t* out_len);
+
+// Call by stable numeric slot (preferred path for performance and diagnostics).
+int32_t nyrt_host_call_slot(uint64_t handle, uint64_t selector_id,
+                            const uint8_t* args_ptr, size_t args_len,
+                            uint8_t* out_ptr, size_t* out_len);
+
+#ifdef __cplusplus
+}
+#endif
+