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/MAKEFILE

@@ -9,7 +9,7 @@ CFLAGS := -target x86_64-unknown-none -std=c11 -ffreestanding -fno-builtin -fno-
 ASFLAGS := -target x86_64-unknown-none -ffreestanding -fno-pic -fno-pie -mcmodel=kernel -mno-red-zone -mno-sse -mno-sse2 -mno-mmx -msoft-float -m64 -Iinclude -I../utsm-ipc
 LDFLAGS := -nostdlib -static -z max-page-size=0x1000 -T linker.ld
 
-C_SOURCES := $(wildcard arch/x86_64/*.c kernel/*.c runtime/*.c mm/*.c core/*.c crypto/*.c pckc/*.c utrw/*.c drr/*.c sched/*.c dkm/*.c test/*.c vmm/*.c pe/*.c)
+C_SOURCES := $(wildcard arch/x86_64/*.c kernel/*.c runtime/*.c mm/*.c core/*.c crypto/*.c pckc/*.c utrw/*.c drr/*.c sched/*.c dkm/*.c test/*.c vmm/*.c pe/*.c brand/*.c pkg/*.c)
 S_SOURCES := $(wildcard arch/x86_64/*.S vmm/*.S sched/*.S)
 OBJECTS := $(C_SOURCES:.c=.o) $(S_SOURCES:.S=.o)
 DEPS := $(C_SOURCES:.c=.d)