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/DKM/virtio_net/virtio_net.c

@@ -775,19 +775,21 @@ static void virtio_net_selftest(void) {
     log_hex("[virtio_net] selftest rx frames seen=", frames);
 }
 
-/* ================= stub（初始化失败时的安全占位，与历史行为一致） ================= */
+/* ================= stub（初始化失败时的安全占位） =================
+ * 严格错误策略插桩：占位不再静默丢包/静默无数据——一旦被上层调用
+ * （即有人真的把流量交给未协商 virtqueue 的设备），立即莲花 panic。
+ * 正常路径 netman 因 flags 缺 LINK_UP 不会选中本驱动，stub 不触发。 */
 
 static int virtio_net_tx_stub(void *ctx, const void *packet, u32 length) {
-    (void)ctx;
-    (void)packet;
-    log_hex("[virtio_net] tx stub: packet dropped, len=", length);
+    (void)ctx; (void)packet;
+    log_hex("[virtio_net] tx stub hit, len=", length);
+    g_log->panic("VNET-E01 TX VIRTQUEUE NOT IMPLEMENTED (stub tx called)");
     return 0;
 }
 
 static int virtio_net_rx_poll_stub(void *ctx, void *buffer, u32 capacity, u32 *out_length) {
-    (void)ctx;
-    (void)buffer;
-    (void)capacity;
+    (void)ctx; (void)buffer; (void)capacity;
+    g_log->panic("VNET-E02 RX VIRTQUEUE NOT IMPLEMENTED (stub rx called)");
     if (out_length) *out_length = 0;
     return 0;
 }