starkernel: item 3.8 -- VM identifiers as UUID/GUID

Punch list §25 item 3.8 complete. Added after starting item 4.1
surfaced the need to thread a vm_id into stadium_admit()'s new quota
parameter; Captain Bob ruled UUID/GUID rather than keeping the
narrower uint32_t.

New VMUuid type (vm_uuid.h/vm_uuid.c): two uint64_t halves, RFC-4122-
shaped for logging. Not real randomness -- checked directly against
QEMU 10.2.1's actual CPU feature set: amd64 RDRAND and riscv64 Zkr are
both real, available features here; aarch64 has no RNG property on any
CPU model including "max" (verified exhaustively via QMP
query-cpu-model-expansion). Captain Bob ruled a uniform fallback
across all three ISAs rather than a per-architecture split.

Fallback is a deterministic PRNG (splitmix64) seeded from the Mama
capsule's content hash, pre-filling a 16-entry FIFO pool at boot and
refilling with another batch of the same stream when exhausted --
exactly the shape requested. Same capsule booted twice produces the
same id sequence, preserving the dict_hash reproducibility this
session has relied on throughout.

Hera keeps a fixed, reserved all-zero id, not drawn from the pool --
capsule_birth.c uses vm_id == 0 as a load-bearing sentinel in three
places (KILL protection x2, fleet heat-fanout parent-chain
terminator), found by reading before writing any code.

Two real sentinel-collision bugs caught before shipping, same class as
STADIUM_CONTAINS_NONE: vm_uuid_none() (all-ones, not all-zero) for
"not yet assigned"/"no VM" placeholders; confirmed item 3.7's quota
table already used an in_use boolean rather than a vm_id sentinel, so
no second collision was actually possible there -- the dead,
never-referenced STADIUM_QUOTA_SLOT_EMPTY macro was removed.

Blast radius larger than first scoped, flagged mid-work rather than
silently absorbed: capsule_vm_physics.c/.h (the fleet heat-transfer
layer item 2.1 modified earlier this session) has its own vm_id-keyed
node table and walks parent_vm_id chains through the same identity
space, so it needed the same change, plus its callers in
mama_forth_words.c and sk_vm_bootstrap.c.

One live FORTH word contract changed, by explicit ruling: CAPSULE-BIRTH
was ( capsule-id -- vm-id ), a single cell -- can't hold 128 bits.
Captain Bob picked pushing two cells ("there is doubles support in the
FORTH std word set anyway"): ( capsule-id -- vm-id-hi vm-id-lo ).
MAMA-VM-ID changed the same way: ( -- 0 0 ).

Verified: full (not standalone-file) kernel rebuild to catch cross-file
breakage given the size of this change -- it surfaced the
capsule_vm_physics.c blast radius a narrower check would have missed.
Three-architecture boot (amd64, aarch64, riscv64), all reaching ok>
with identical dict_hash=0x3d4e1daf289da94f matching the item-3.7
baseline.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

include/starkernel/capsule_vm_physics.h

@@ -41,6 +41,7 @@
 #define STARKERNEL_CAPSULE_VM_PHYSICS_H
 
 #include <stdint.h>
+#include "starkernel/vm_uuid.h" /* VMUuid -- FABRIC.md item 3.8 */
 
 #ifdef __cplusplus
 extern "C" {
@@ -55,7 +56,7 @@ extern "C" {
  *
  * @param vm_id  Registry VM ID assigned at birth
  */
-void vm_physics_init(uint32_t vm_id);
+void vm_physics_init(VMUuid vm_id);
 
 /**
  * vm_physics_retire - Remove a killed VM, returning its heat to Hera
@@ -70,7 +71,7 @@ void vm_physics_init(uint32_t vm_id);
  *
  * @param vm_id  Registry VM ID of the VM being killed
  */
-void vm_physics_retire(uint32_t vm_id);
+void vm_physics_retire(VMUuid vm_id);
 
 /**
  * vm_physics_touch - Record real dispatch activity against a VM
@@ -89,7 +90,7 @@ void vm_physics_retire(uint32_t vm_id);
  *
  * @param vm_id   Registry VM ID being dispatched to
  */
-void vm_physics_touch(uint32_t vm_id);
+void vm_physics_touch(VMUuid vm_id);
 
 /**
  * vm_physics_tick - Heartbeat-gated inference pass
@@ -147,7 +148,7 @@ uint64_t vm_physics_fleet_heat_sum(void);
  * @param vm_id  Registry VM ID
  * @return       execution_heat_q48, or 0 if vm_id is unknown or not live
  */
-uint64_t vm_physics_heat_of(uint32_t vm_id);
+uint64_t vm_physics_heat_of(VMUuid vm_id);
 
 /**
  * vm_physics_conserved - Conservation check