fix(paging): drop high-half stack clone that faulted during runtime spawn

VKernel/Kernel/paging/paging.vp

@@ -697,12 +697,10 @@ def clone_for_process(isolate_vaddr: uint64, stack_vaddr: uint64 = 0) -> uint64:
     for i in range(512):
         new_pt_page.entries[i] = kernel_pt.entries[i] & ~PTE_USER
     new_pd_page.entries[pd_idx] = (uint64(new_pt_page) & ~uint64(0xFFF)) | (kernel_pd.entries[pd_idx] & uint64(0xFFF) & ~PTE_USER)
-    # 用户栈（含 user thread 栈）都落在同一个高地址区；必须为每个进程私有化
-    # 对应的 PML4/PDP/PD/PT 分支，否则新进程映射栈会覆盖父进程的栈 PTE。
-    if stack_vaddr != 0:
-        _clone_vaddr(new_pml4_page, stack_vaddr)
-        _clone_vaddr(new_pml4_page, stack_vaddr - uint64(0x200000))
-        _clone_vaddr(new_pml4_page, stack_vaddr - uint64(0x400000))
+    # 以 kernel PML4 为模板时，PML4[511]（用户栈所在高半区）通常没有映射；
+    # 之后 _elf_entry_wrapper 里的 MapPage 会为该进程新建私有 PDP/PD/PT。
+    # 不要在这里额外 clone 高半区：kernel PML4[511] 可能含有 1GiB/大页或
+    # 非用户映射，强行拆分会在 clone 阶段访问用户栈 VA 触发内核 #PF。
     return uint64(new_pml4_page)
 
 # Deep-copy every USER mapping from src into dst (dst must already contain the