refactor: 进一步拆分函数执行逻辑以简化主流程

crates/oxide_vm/src/dispatch/arithmetic.rs

@@ -1 +1,21 @@
-// dispatch helper functions extracted from vm.rs
+use crate::coercion;
+use crate::vm::Vm;
+use oxide_types::value::JsValue;
+
+impl Vm {
+    #[inline(always)]
+    pub(crate) fn dispatch_add(&mut self, rd: usize, a: usize, b: usize) {
+        let lhs = self.regs[a];
+        let rhs = self.regs[b];
+        if lhs.is_string() || rhs.is_string() {
+            let ls = coercion::to_string(self.kernel.string_forge().as_ref(), lhs);
+            let rs = coercion::to_string(self.kernel.string_forge().as_ref(), rhs);
+            let concat = format!("{ls}{rs}");
+            self.regs[rd] = self.intern(&concat);
+        } else {
+            let ln = coercion::to_number(lhs, self.kernel.string_forge().as_ref());
+            let rn = coercion::to_number(rhs, self.kernel.string_forge().as_ref());
+            self.regs[rd] = JsValue::float(ln + rn);
+        }
+    }
+}