refactor(compiler): 拆分 oxide_emit 为独立 emit pass crate（依赖倒置）

crates/oxide_emit/src/stmt/declaration/class_decl.rs

@@ -0,0 +1,30 @@
+use crate::{CompileCtx, Emitter};
+use oxide_ir::inst::Inst;
+use oxide_ir::operand::Operand;
+use oxide_bytecode::opcode::OpCode;
+use oxide_parser::{Statement, VariableDeclarationKind};
+
+impl Emitter {
+    pub(crate) fn emit_class_declaration_statement(
+        &self, stmt: &Statement, ctx: &mut CompileCtx,
+    ) -> Result<Option<u8>, String> {
+        let Statement::ClassDeclaration(class) = stmt else {
+            return Err("ClassDeclaration without name".into());
+        };
+        let name = class
+            .id
+            .as_ref()
+            .map(|id| id.name.to_string())
+            .ok_or_else(|| "ClassDeclaration without name".to_string())?;
+        let var_reg = ctx.alloc_reg();
+        ctx.declare(&name, var_reg, VariableDeclarationKind::Let, false)?;
+        ctx.init_var(&name);
+        let ctor_reg = self.emit_class(class, ctx)?;
+        if let Some(&cell_idx) = ctx.captured_bindings.get(&name) {
+            ctx.inst(Inst::new(OpCode::MAKE_CELL, Operand::Reg(var_reg as u32), Operand::Imm(cell_idx as u16), Operand::None));
+        } else {
+            ctx.inst(Inst::new(OpCode::STORE_VAR, Operand::Reg(var_reg as u32), Operand::Reg(ctor_reg as u32), Operand::None));
+        }
+        Ok(None)
+    }
+}