fix(type): const 等限定联合不再被误判为 str*/bytes*

_is_ptr_element_annotation 原先只要注解联合里出现 str/bytes 就返回 1（按 i8** 处理，
8 字节元素步长），于是 const str（t.CConst | str，实际仍是 i8*）的下标取到的是指针。
现在要求联合必须带 CPtr 标记（真正的 str*/bytes*）才判定；模块级全局的同一处逻辑
（TranslatorGenMixin）同步收紧。新增 _annotation_has_cptr_marker 供两处复用。

复现：def F(p: str) -> int: / path: const str = p / ch: char = path[i]
      -> CastError 指针转整数（形参位置的 const str 一直正常，仅局部/全局错）

App/lib/core/Gen/AssignGenMixin.vp

@@ -517,6 +517,24 @@ novirtual class AssignGenMixin:
             if self._annotation_contains_name(bop.right, name) != 0: return 1
         return 0
 
+    def _annotation_has_cptr_marker(self, annot: ast.AST*) -> int:
+        """Return 1 if the annotation union carries a CPtr marker (the star form `<base> | t.CPtr`)."""
+        if annot is None: return 0
+        k: int = annot.kind()
+        if k == ast.ASTKind.Attribute:
+            at: ast.Attribute* = ast.Attribute*(annot)
+            if at.attr is not None and string.strcmp(at.attr, "CPtr") == 0: return 1
+            return 0
+        if k == ast.ASTKind.Name:
+            nm: ast.Name* = ast.Name*(annot)
+            if nm.id is not None and string.strcmp(nm.id, "CPtr") == 0: return 1
+            return 0
+        if k == ast.ASTKind.BinOp:
+            bop: ast.BinOp* = ast.BinOp*(annot)
+            if self._annotation_has_cptr_marker(bop.left) != 0: return 1
+            if self._annotation_has_cptr_marker(bop.right) != 0: return 1
+        return 0
+
     # _is_ptr_element_annotation - check whether an annotation is bytes* or str*
     # bytes*/str* => 8-byte element stride (i8**); char*/int8* => 1-byte stride.
     def _is_ptr_element_annotation(self, annot: ast.AST*) -> int:
@@ -526,8 +544,12 @@ novirtual class AssignGenMixin:
         if k != ast.ASTKind.BinOp: return 0
         bop: ast.BinOp* = ast.BinOp*(annot)
         if bop.op != ast.OpKind.BitOr: return 0
-        if self._annotation_contains_name(annot, "str") != 0: return 1
-        if self._annotation_contains_name(annot, "bytes") != 0: return 1
+        # str/bytes are already i8*; only the union WITH a pointer marker (str*/bytes*) is i8** and
+        # needs 8-byte element slots. A union that merely carries them (e.g. `const str`, which is
+        # t.CConst | str and stays i8*) must keep the 1-byte stride.
+        if self._annotation_has_cptr_marker(annot) != 0:
+            if self._annotation_contains_name(annot, "str") != 0: return 1
+            if self._annotation_contains_name(annot, "bytes") != 0: return 1
         # Generic type param / nested union | t.CPtr: scalars use their own size, pointers use 8-byte slots
         if self._is_generic_tp_or_nested(bop.left) != 0 or self._is_generic_tp_or_nested(bop.right) != 0:
             gp_nm: str = None

App/lib/core/Gen/TranslatorGenMixin.vp

@@ -859,8 +859,9 @@ novirtual class TranslatorGenMixin:
                     if aa_ml.annotation.kind() == ast.ASTKind.BinOp:
                         bop_ml: ast.BinOp* = ast.BinOp*(aa_ml.annotation)
                         if bop_ml.op == ast.OpKind.BitOr:
-                            if self.Gen.AssignGen._annotation_contains_name(aa_ml.annotation, "str") != 0 or self.Gen.AssignGen._annotation_contains_name(aa_ml.annotation, "bytes") != 0:
-                                self.Gen.VarGen.set_var_ptr_element(trans.SymTab, var_name)
+                            if self.Gen.AssignGen._annotation_has_cptr_marker(aa_ml.annotation) != 0:
+                                if self.Gen.AssignGen._annotation_contains_name(aa_ml.annotation, "str") != 0 or self.Gen.AssignGen._annotation_contains_name(aa_ml.annotation, "bytes") != 0:
+                                    self.Gen.VarGen.set_var_ptr_element(trans.SymTab, var_name)
             return 1
         return 0