debug(_withcontent): 临时 [wdbg] 诊断 provider 栈运行时状态

TLS 守卫/strcmp/IR 均正确但 Test 9 仍 find 返回 NULL，加运行时诊断：
get_stack 打印 tls 索引与栈指针（观察是否每次 NEW）、push 打印 field/ptr/top、
find 打印 field/top/HIT。重编 Test 跑一轮后删除。

includes/_withcontent.vp

@@ -37,16 +37,21 @@ def _get_stack() -> _ProviderStack | t.CPtr:
     """Obtain current thread's provider stack. Allocate one if none exists."""
     _init_tls()
     stack: _ProviderStack | t.CPtr = TlsGetValue(_tls_index)
+    stdio.printf("[wdbg] get_stack tls=%llu stack=%p\n",
+                 t.CUInt64T(_tls_index), stack)
     if stack == None:
         stack = stdlib.malloc(_ProviderStack.__sizeof__())
         string.memset(stack, 0, _ProviderStack.__sizeof__())
         TlsSetValue(_tls_index, stack)
+        stdio.printf("[wdbg] get_stack NEW stack=%p\n", stack)
     return stack
 
 
 def _push_provider(field_name: str, ptr: t.CPtr):
     """Push a provider (field_name, ptr) onto the stack."""
     stack: _ProviderStack | t.CPtr = _get_stack()
+    stdio.printf("[wdbg] push field=%s ptr=%p top=%lu\n",
+                 field_name, ptr, stack.top)
     if stack.top >= _MAX_PROVIDER_DEPTH:
         stdio.printf("[with] ERROR: provider stack overflow (depth=%lu, max=%d), field '%s' not injected\n", stack.top, _MAX_PROVIDER_DEPTH, field_name)
         return
@@ -66,10 +71,12 @@ def _find_provider(field_name: str) -> t.CPtr:
     """Search for matching field_name starting from stack top.
     Return associated pointer, or NULL if no match found."""
     stack: _ProviderStack | t.CPtr = _get_stack()
+    stdio.printf("[wdbg] find field=%s top=%lu\n", field_name, stack.top)
     for i in range(stack.top - 1, -1, -1):
         # 字段名用 strcmp 内容比较：编译器对每次 create_global_string 生成
         # 独立的字符串常量（TPV 不去重），push/find 的指针地址不同，
         # 指针 == 永假会导致 provider 匹配失败（__mbuddy__ 注入不上）。
         if string.strcmp((str)(stack.names[i]), field_name) == 0:
+            stdio.printf("[wdbg] find HIT i=%d ptr=%p\n", i, stack.ptrs[i])
             return stack.ptrs[i]
     return None