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

src/starkernel/kernel_main.c

@@ -21,6 +21,7 @@
 #error "__STARKERNEL__ must be defined for kernel build"
 #endif
 
+#include <string.h>
 #include "uefi.h"
 #include "console.h"
 #include "arch.h"
@@ -65,6 +66,7 @@ EFI_RUNTIME_SERVICES *g_sk_runtime_services = NULL;
 #include "starkernel/pci.h"
 #include "starkernel/virtio_blk.h"
 #include "starkernel/virtio_rng.h"
+#include "starkernel/ed25519.h"
 #include "starkernel/virtio_input.h"
 #include "starkernel/xhci_driver.h"
 #include "block_subsystem.h"

src/starkernel/vm/vm_core.c

@@ -266,6 +266,22 @@ void vm_set_base(VM* vm, unsigned b)
     vm->base = (cell_t)b; /* host mirror */
 }
 
+/* Kernel-side copy of src/vm.c's vm_zuse_cert_install() -- the kernel
+ * build excludes src/vm.c entirely (VM_EXCLUDE in Makefile.starkernel;
+ * see vm_set_base() above for the same duplication pattern already
+ * established), so any src/vm.c function the kernel needs to call gets
+ * its own copy here. See src/vm.c's version for the full rationale
+ * (why this is a VM struct field with no FORTH word, not a CONSTANT). */
+int vm_zuse_cert_install(VM* vm, const uint8_t seed[32], const uint8_t pubkey[32])
+{
+    if (!vm) return -1;
+    if (vm->zuse_cert_installed) return -1;
+    memcpy(vm->zuse_cert_seed, seed, 32);
+    memcpy(vm->zuse_cert_pubkey, pubkey, 32);
+    vm->zuse_cert_installed = 1;
+    return 0;
+}
+
 /* ====================== VM init / teardown ======================= */
 void vm_cleanup(VM* vm)
 {