refactor(dev): unify user-facing diagnostics

src/mir/RegAlloc.cpp

@@ -2,6 +2,8 @@
 
 #include <stdexcept>
 
+#include "utils/Log.h"
+
 namespace mir {
 namespace {
 
@@ -24,7 +26,7 @@ void RunRegAlloc(MachineFunction& function) {
   for (const auto& inst : function.entry().instructions()) {
     for (const auto& operand : inst.operands()) {
       if (operand.kind() == Operand::Kind::Reg && !IsAllowedReg(operand.reg())) {
-        throw std::runtime_error("Lab3 MVP 后端发现未预着色的寄存器");
+        throw std::runtime_error(FormatError("mir", "寄存器分配失败"));
       }
     }
   }