Phase 12 TypeBox統合ABI設計完了: C ABI + Nyash ABI革命的統合

主な成果:
- TypeBox（型情報をBoxとして扱う）による統合ABI設計
- C ABI + Nyash ABIの完全統合仕様書作成
- 3大AI専門家（Gemini/Codex/ChatGPT5）による検証済み
- ChatGPT5の10個の安全性改善提案を反映
- README.mdのドキュメント更新（全起点から到達可能）

MapBox拡張:
- string型キーサポート（従来のi64に加えて）
- remove/clear/getOr/keysStr/valuesStr/toJson実装
- keys()/values()のランタイムシムサポート（TypeBox待ち）

その他の改善:
- Phase 11.9（文法統一化）ドキュメント追加
- Phase 16（FoldLang）ドキュメント追加
- 非同期タイムアウトテスト追加
- 各種ビルド警告（未使用import等）は次のリファクタリングで対応予定

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

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

src/jit/lower/core.rs

@@ -779,6 +779,52 @@ impl LowerCore {
                         if dst.is_some() { b.emit_const_i64(0); }
                     }
                 } else {
+                    // Await bridge: env.future.await(fut) → await_h + ok_h/err_h select
+                    if iface_name == "env.future" && method_name == "await" {
+                        // Load future: prefer param, then local, then known const, else -1 scan
+                        if let Some(arg0) = args.get(0) {
+                            if let Some(pidx) = self.param_index.get(arg0).copied() {
+                                b.emit_param_i64(pidx);
+                            } else if let Some(slot) = self.local_index.get(arg0).copied() {
+                                b.load_local_i64(slot);
+                            } else if let Some(v) = self.known_i64.get(arg0).copied() {
+                                b.emit_const_i64(v);
+                            } else {
+                                b.emit_const_i64(-1);
+                            }
+                        } else {
+                            b.emit_const_i64(-1);
+                        }
+                        // await_h → handle (0 on timeout)
+                        b.emit_host_call(crate::jit::r#extern::r#async::SYM_FUTURE_AWAIT_H, 1, true);
+                        let hslot = { let id = self.next_local; self.next_local += 1; id };
+                        b.store_local_i64(hslot);
+                        // ok_h(handle)
+                        b.load_local_i64(hslot);
+                        b.emit_host_call(crate::jit::r#extern::result::SYM_RESULT_OK_H, 1, true);
+                        let ok_slot = { let id = self.next_local; self.next_local += 1; id };
+                        b.store_local_i64(ok_slot);
+                        // err_h(0) => Timeout
+                        b.emit_const_i64(0);
+                        b.emit_host_call(crate::jit::r#extern::result::SYM_RESULT_ERR_H, 1, true);
+                        let err_slot = { let id = self.next_local; self.next_local += 1; id };
+                        b.store_local_i64(err_slot);
+                        // Select by (handle==0)
+                        b.load_local_i64(hslot);
+                        b.emit_const_i64(0);
+                        b.emit_compare(crate::jit::lower::builder::CmpKind::Eq);
+                        b.load_local_i64(err_slot);
+                        b.load_local_i64(ok_slot);
+                        b.emit_select_i64();
+                        if let Some(d) = dst {
+                            self.handle_values.insert(*d);
+                            let slot = *self.local_index.entry(*d).or_insert_with(|| { let id = self.next_local; self.next_local += 1; id });
+                            b.store_local_i64(slot);
+                        } else {
+                            // drop
+                        }
+                        return Ok(());
+                    }
                     // Async spawn bridge: env.future.spawn_instance(recv, method_name, args...)
                     if iface_name == "env.future" && method_name == "spawn_instance" {
                         // Stack layout for hostcall: argc_total, a0(recv), a1(method_name), a2(first payload)