feat: with 语句、成员位/移位复合赋值、CALL_NATIVE 无目标修复

with 语句：新增 emit 支持，with 体内自由标识符动态解析（对象属性优先，
回退外层），支持读/写/复合赋值/自增自减/delete/var 初始化动态化，
TO_OBJECT opcode 处理原始值对象，顶层 this 绑定全局对象。

复合赋值：新增 6 个 COMPOUND_MEMBER_BIT_* opcode 支持成员位/移位复合赋值，
修复 computed member 复合赋值覆盖 bug，with 内标识符复合赋值动态化。

CALL_NATIVE：实现全局 isNaN/isFinite 并绑定，用户覆盖 builtin 名时
回退通用调用路径而非报错，局部遮蔽 builtin 名走普通 CALL。

test262: with 34 pass（基线 0），compound-assignment 320 pass（基线 223）

crates/oxide_emit/src/closure.rs

@@ -81,6 +81,7 @@ impl Emitter {
                     }
                 }
                 Statement::LabeledStatement(ls) => self.collect_decl_names_stmt(std::slice::from_ref(&ls.body), out),
+                Statement::WithStatement(ws) => self.collect_decl_names_stmt(std::slice::from_ref(&ws.body), out),
                 _ => {}
             }
         }
@@ -202,6 +203,10 @@ impl Emitter {
                 }
             }
             Statement::LabeledStatement(ls) => self.collect_capture_names_stmt(&ls.body, ref_set, shadow, out),
+            Statement::WithStatement(ws) => {
+                self.collect_capture_names_expr(&ws.object, ref_set, shadow, out);
+                self.collect_capture_names_stmt(&ws.body, ref_set, shadow, out);
+            }
             _ => {}
         }
     }
@@ -525,6 +530,10 @@ impl Emitter {
                 }
             }
             Statement::LabeledStatement(ls) => self.collect_captured_stmt(&ls.body, own, out),
+            Statement::WithStatement(ws) => {
+                self.collect_captured_expr(&ws.object, own, out);
+                self.collect_captured_stmt(&ws.body, own, out);
+            }
             _ => {}
         }
     }