feat(TPC): 拓展 isinstance 跨模块支持

vtable linkage 改默认外部强定义（含 initializer 自动归一为空），跨模块可引用 sha1.Class_Vtable；外部引用声明为 i8* 避免 array 类型不匹配；_ResolveVtableAddr 增加 CVTable 状态检查，NoVTable 类回退编译时静态判断避免坏引用。新增 geom_lib.vp 跨模块测试库，main.vp 增加跨模块继承/运行时多态/NoVTable 场景。

Test/IsinstanceTest/App/geom_lib.vp

@@ -0,0 +1,43 @@
+import t
+from t import CInt
+
+
+# ============================================================
+# 跨模块 isinstance 测试库
+#
+# 供 main.vp import 使用：验证 isinstance 对"定义在其他模块
+# 的类"也能正确比较（对象 vtable 指针跨 obj 链接解析）。
+# ============================================================
+
+
+@t.CVTable
+class Shape:
+    def area(self) -> CInt:
+        return 0
+
+
+@t.CVTable
+class Circle(Shape):
+    r: CInt
+
+    def __init__(self, r: CInt):
+        self.r = r
+
+    def area(self) -> CInt:
+        return self.r
+
+
+@t.CVTable
+class Square(Shape):
+    s: CInt
+
+    def __init__(self, s: CInt):
+        self.s = s
+
+    def area(self) -> CInt:
+        return self.s
+
+
+@t.NoVTable
+class PlainShape:
+    tag: CInt

Test/IsinstanceTest/App/main.vp

@@ -1,6 +1,7 @@
 from stdint import *
 import t, c
 import testcheck
+import geom_lib
 
 
 # ============================================================
@@ -123,5 +124,29 @@ def main() -> CInt | CExport:
                     "isinstance NoVTable FAILED")
     testcheck.check(p.v == 42, "NoVTable 字段正常 OK", "NoVTable 字段 FAILED")
 
+    # --- 6. 跨模块 isinstance（vtable 跨 obj 链接解析） ---
+    cc: geom_lib.Circle | CPtr = geom_lib.Circle(5)
+    testcheck.check(isinstance(cc, geom_lib.Circle) == 1,
+                    "跨模块 isinstance 自身 OK", "跨模块 isinstance 自身 FAILED")
+    testcheck.check(isinstance(cc, geom_lib.Shape) == 1,
+                    "跨模块 isinstance 子类→基类 OK", "跨模块 isinstance 子类→基类 FAILED")
+    testcheck.check(isinstance(cc, geom_lib.Square) == 0,
+                    "跨模块 isinstance 不匹配 OK", "跨模块 isinstance 不匹配 FAILED")
+    sq: geom_lib.Square | CPtr = geom_lib.Square(3)
+    testcheck.check(isinstance(sq, geom_lib.Shape) == 1,
+                    "跨模块 Square→Shape OK", "跨模块 Square→Shape FAILED")
+    testcheck.check(isinstance(sq, geom_lib.Circle) == 0,
+                    "跨模块 Square vs Circle OK", "跨模块 Square vs Circle FAILED")
+    shp: geom_lib.Shape | CPtr = (geom_lib.Shape | CPtr)(cc)
+    testcheck.check(isinstance(shp, geom_lib.Circle) == 1,
+                    "跨模块运行时多态 OK", "跨模块运行时多态 FAILED")
+    testcheck.check(shp.area() == 5, "跨模块虚方法分派 OK", "跨模块虚方法分派 FAILED")
+    testcheck.check(cc.area() == 5, "跨模块 Circle.area OK", "跨模块 Circle.area FAILED")
+
+    # --- 7. NoVTable 跨模块静态判断 ---
+    ps: geom_lib.PlainShape | CPtr = geom_lib.PlainShape()
+    testcheck.check(isinstance(ps, geom_lib.PlainShape) == 1,
+                    "跨模块 NoVTable 静态 OK", "跨模块 NoVTable 静态 FAILED")
+
     testcheck.ok("isinstance 全部测试完成")
     return testcheck.end()