Phase 8 C (2/n): expand cert storage; NVRAM persistence crashed, reverted

Cert storage expanded from the old 16-byte placeholder to a real
32-byte seed + 32-byte pubkey. vm_zuse_cert_install() now has a
kernel-side duplicate in src/starkernel/vm/vm_core.c -- the kernel
build's VM_EXCLUDE list drops src/vm.c entirely (same reason
vm_set_base() already has two independent copies), so the hosted-only
version added earlier this session was never actually linked into the
kernel. FORTH-side ZUSE-CERT-LO@/HI@ replaced with ZUSE-PUBKEY@ (i -- u)
over the public half only; ACL-ZUSE-BOOT now checks
ZUSE-CERT-INSTALLED? before authenticating instead of unconditionally.

Attempted NVRAM-based persistence (GetVariable/SetVariable) for the
first-boot mint flow: page-faulted inside OVMF's variable service
(CR2 in the flash MMIO window). Moving the call site to match the one
proven-safe existing SetVariable call site in this codebase produced
the identical crash -- not a timing issue. Localized with debug
markers (one boot): GetVariable works; SetVariable with real data
never returns. The existing "working" precedent call is actually a
delete-of-nonexistent-variable (size=0, data=NULL), a cheaper path
that never touches flash, so it proved nothing about real writes.
Root cause: this kernel's VMM never maps the region OVMF's variable
service needs for real flash writes -- a genuine gap in UEFI runtime-
services support, not Zuse-specific, and not obviously fixable in a
3-arch-uniform way (flash window location is firmware/arch-specific).

Independently, storing the raw seed in RUNTIME_ACCESS NVRAM would have
been a real security defect regardless of the crash -- readable by any
later-loaded UEFI app or the booted OS.

Reverted to a known-safe state: all NVRAM/mint code removed from
kernel_main.c, init.4th's ACL.4th line back to its documented
commented-out default. Verified clean compile and clean boot on all
three architectures. Cert storage expansion (the part that works)
stays. A dedicated system-identity disk (virtio-blk, already proven
for writes via Artemis) is the recommended next substrate -- not yet
decided or built. Full investigation documented in FABRIC-3.md.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01U14ET9CWAtbQMbYqomKgXd

include/starkernel/uefi.h

@@ -624,6 +624,13 @@ typedef void (EFIAPI *EFI_RESET_SYSTEM)(
 /* NVRAM variable names (UCS-2 string literals) */
 #define SF_VAR_BOOT_ARGS   L"StarForthBootArgs"
 #define SF_VAR_REBOOT_TRIES L"StarForthRebootTries"
+#define SF_VAR_ZUSE_CERT   L"StarForthZuseCert" /* 64 bytes: 32-byte Ed25519
+                                                  * seed || 32-byte pubkey.
+                                                  * Written exactly once
+                                                  * (Phase 8 first-boot mint,
+                                                  * see FABRIC-3.md) --
+                                                  * presence means the fuse
+                                                  * is already blown. */
 
 /* ---- BootInfo extension ------------------------------------------------ */
 #include "kernel_args.h"