feat: SKEL skeleton instrumentation - designed-but-unimplemented paths panic

- hypercall.c: 5 Phase 1.3 stubs -> HCALL-E01..E05 panic (no NOSYS return)
- drr_stub.c: snapshot alloc fail -> DRR-E01; new skeletons DRR-E02 root key
  seal, DRR-E03 task kill crypto erase, DRR-E04/E05 segment/system rollback,
  DRR-E06/E07 driver recovery ops dispatch
- sched.c: enable fail -> SCH-E02 panic (no silent demo skip)
- dkm/kernel_api.c: D1 hot-unload DKM-E01, D2 bare code loader DKM-E02,
  SIPI AP wake DKM-E03 skeletons
- virtio_net tx/rx stubs -> VNET-E01/E02; ath9k tx stub -> ATH-E01;
  xhci port reset -> XHC-E01; nvme MSI/MSI-X fail -> NVME-E01..E03 (no
  silent polling downgrade); e1000 MAC fallback -> E1K-E01
- pe_shim unimpl API -> PE-E01; PE ordinal import -> PE-E02
- kernel/main.c: lib sync / vscode install fail -> LNX-E01/E02
- NEW brand/brand.c (E1 boot anim BRAND-E01, E2 time egg BRAND-E02) and
  pkg/pkg.c (pacman skeleton PKG-E01..03), wired into UTSM MAKEFILE
- Deliberate design-internal fallbacks kept and documented (VMX skip,
  bzImage skip, KDE fallback, boot-module fallback, apic->PIC route)

CODE/UTSM/pe/pe_shim.c

@@ -29,6 +29,7 @@
 #include "../include/utsm/pe.h"   /* P5: pe_window_host */
 #include <utsm/arena.h>
 #include <utsm/log.h>
+#include <utsm/panic.h>
 #include <utsm/types.h>
 #include "../arch/x86_64/limine.h"
 
@@ -1753,11 +1754,15 @@ static u64 __attribute__((ms_abi)) shim_SetDIBitsToDevice(
     return copied;
 }
 
-/* 未实现 stub(64位)— 日志告警(含调用点返回地址)并返回 0 */
+/* 未实现 stub(64位)——严格错误策略插桩：PE 应用调到 shim 表未覆盖的
+ * API = 未实现路径，按零降级原则 panic（PE-E01），不再告警返回 0。
+ * shim 表没有的 API 一旦被调用，PE 程序的语义已经是错的。 */
 static u64 __attribute__((ms_abi)) shim_unimpl64(u64 a0, u64 a1, u64 a2, u64 a3) {
     (void)a0; (void)a1; (void)a2; (void)a3;
-    log_warn("[PE] unimplemented API called");
+    log_error("[PE] unimplemented API called");
     log_hex64("[PE]   caller rip=", (u64)__builtin_return_address(0));
+    panic_full("PE-E01 UNSHIMMED API CALLED",
+               "PE app imported an API outside the shim table: not implemented", 0);
     return 0;
 }