feat(gen): range 边界与循环变量统一提升到至少 i32（取消 u8/u16 循环变量档），u64 边界保持 i64

App/lib/core/Gen/Stmt/StmtGenCifMixin.vp

@@ -1115,8 +1115,28 @@ novirtual class StmtGenCifMixin:
                     skc_r: ast.Constant* = ast.Constant*(step_arg_node)
                     if skc_r.int_val < 0: step_neg_const = 1
 
-        # 3.5 loop-var storage width follows range arg type (u64→i64 / u16→i16 / u8→i8 / else i32);
-        # a fixed i32 alloca truncates uint64 bounds. Applies only to undeclared loop vars.
+        # 3.4 range 边界统一提升到**至少 i32**（仿 C 整数提升）：i8/i16 边界不再以窄位宽参与比较
+        # 与自增。拓宽方向由 coerce_to_type → should_zext_widen 决定：非负 define 常量是**无符号
+        # 位模式**（Debugger/define-constants.md §7.2），必须 zext（define N = 50000 → 16 位 0xC350
+        # → 50000，而非 sext 成 -15536）。u64 边界保持 i64（不动，避免截断）。
+        if stop_val is not None and stop_val.Ty is not None:
+            sb_p4: int = self.Gen.ExprGenBase.get_llvm_type_bits(stop_val.Ty)
+            if sb_p4 != 0 and sb_p4 < 32:
+                nd_s4: ast.AST* = args.get(0)
+                if arg_count >= 2: nd_s4 = args.get(1)
+                stop_val = self.Gen.ExprGenBase.coerce_to_type(builder, stop_val, i32_ty, nd_s4, trans)
+        if start_val is not None and start_val.Ty is not None:
+            sa_p4: int = self.Gen.ExprGenBase.get_llvm_type_bits(start_val.Ty)
+            if sa_p4 != 0 and sa_p4 < 32:
+                start_val = self.Gen.ExprGenBase.coerce_to_type(builder, start_val, i32_ty, args.get(0), trans)
+        if step_val is not None and step_val.Ty is not None:
+            sp_p4: int = self.Gen.ExprGenBase.get_llvm_type_bits(step_val.Ty)
+            if sp_p4 != 0 and sp_p4 < 32:
+                step_val = self.Gen.ExprGenBase.coerce_to_type(builder, step_val, i32_ty, args.get(2), trans)
+
+        # 3.5 loop-var storage width: 边界已提升到 ≥i32，所以只有 i64 边界需要 i64 循环变量，
+        # 其余一律 i32（不再有 u16→i16 / u8→i8 档：窄位宽循环变量会把边界截断）。
+        # Applies only to undeclared loop vars.
         loop_store_ty: mlirlite.LLVMType* = i32_ty
         range_arg_bits: int = 0
         if arg_count == 1:
@@ -1128,8 +1148,6 @@ novirtual class StmtGenCifMixin:
             if stop_val is not None and stop_val.Ty is not None: stop_bits_rt = self.Gen.ExprGenBase.get_llvm_type_bits(stop_val.Ty)
             range_arg_bits = start_bits_rt if start_bits_rt > stop_bits_rt else stop_bits_rt
         if range_arg_bits == 64: loop_store_ty = mlirlite.Int64(pool)
-        elif range_arg_bits == 16: loop_store_ty = mlirlite.Int16(pool)
-        elif range_arg_bits == 8: loop_store_ty = mlirlite.Int8(pool)
 
         # 3.6 loop unsignedness: an unsigned loop-var annotation or any unsigned range bound uses
         # icmp ult/ugt instead of slt/sgt (via ExprGenOps._node_type_unsigned).