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/pkg/pkg.c

@@ -0,0 +1,38 @@
+/* ===================================================================
+ *  pkg.c — 包管理器骨架（Pacman 五阶段方案，docs/STATUS.md）
+ *
+ *  设计已定（五阶段：清单 → 仓库索引 → 差分下载 → 安装事务 →
+ *  回滚钩子接 DRR），实现未动。建立代码骨架：调用即莲花 panic，
+ *  零降级零静默。
+ * =================================================================== */
+
+#include <utsm/types.h>
+#include <utsm/panic.h>
+#include <utsm/log.h>
+
+/* 阶段1: 从仓库清单解析包元数据（名称/版本/依赖/文件清单） */
+int pkg_query(const char *name) {
+    (void)name;
+    log_error("[PKG] query requested");
+    panic_full("PKG-E01 PKG QUERY NOT IMPLEMENTED",
+               "pacman-style package query: designed (5-phase), not implemented", 0);
+    return -1;
+}
+
+/* 阶段2+3: 仓库索引 + 差分下载 */
+int pkg_install(const char *name) {
+    (void)name;
+    log_error("[PKG] install requested");
+    panic_full("PKG-E02 PKG INSTALL NOT IMPLEMENTED",
+               "package install transaction: designed (5-phase), not implemented", 0);
+    return -1;
+}
+
+/* 阶段4+5: 安装事务 + DRR 回滚钩子 */
+int pkg_remove(const char *name) {
+    (void)name;
+    log_error("[PKG] remove requested");
+    panic_full("PKG-E03 PKG REMOVE NOT IMPLEMENTED",
+               "package removal + DRR rollback hook: designed (5-phase), not implemented", 0);
+    return -1;
+}