FABRIC-3.8.md Stage FR: VM frame stacks, each frame with an ID

Captain Bob: "give frames IDs and call by ID" -- frames stack per VM, each
with an ID. New vm_frame.h/.c: VMFrameEntry { VMFrameID id; VMUuid vm_id;
kind (INTERPRET/DRAIN/IDLE) }, a growable VMFrameStack embedded as VM.frames
(reserved at birth, freed in vm_cleanup, grown by allocate-copy-free).
vm_interpret() -> vm_interpret_kind() pushes a frame onto the running stack's
owner, holds only its ID, fails closed if it cannot grow, and pops by ID
(mismatch reported as VM FRAME CORRUPTION).

The Stage A/B loose fields are gone and everything is derived from the stack:
- ownership gate: one frame, and it is vm's own
- drain guard: a DRAIN frame for vm already on the running stack
- parked-idle: an IDLE frame the trampoline pushes around its yield
- log attribution: the top frame's vm_id, resolved by ID through the registry
The single saved-and-restored attribution global is removed.

Evidence: the probe baseline on the pre-frame code read HSSAS (the global
named Hestia while Hera resumed). With frames it reads HSHAS on all three
ISAs, with Hestia's top frame IDLE and Hera's frames back to 0; the probe is
reverted. Formal acceptance on all three ISAs: dict_hash identical and
unchanged, zero UNKNOWN WORD, faults, frame corruption or refused interprets,
and the WIREBIND relay 1 2 + . -> 3 works.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/starkernel/vm/switch.c

@@ -133,12 +133,24 @@ void sk_vm_switch_entry(void) {
         if (sk_hermes_drain_checkpoint(self) != 0) {
             continue; /* consumed one message (1 = ok, -1 = payload erred) */
         }
-        self->parked_idle = 1;
-        if (!self->native_switch_back_to ||
-            sk_vm_context_switch(self, self->native_switch_back_to) != 0) {
-            sk_hal_panic("switch trampoline: idle yield failed");
+        /* Stage FR (§3.12): parked-idle is a VM_FRAME_IDLE frame on this VM's
+         * own stack, pushed only around the yield and popped (by ID) on
+         * resume, BEFORE any further drain -- so the drain's own frame is
+         * still the only frame and the ownership gate's exactly-one-frame
+         * rule holds. It records WHERE the VM is parked: an empty stack alone
+         * would also describe Hera parked at an idle point with her REPL call
+         * chain live, which is not "nothing in progress." */
+        {
+            VMFrameID idle_id = vm_frame_push(&self->frames, self->stadium_vm_id, VM_FRAME_IDLE);
+            if (idle_id == 0) {
+                sk_hal_panic("switch trampoline: idle frame push failed");
+            }
+            if (!self->native_switch_back_to ||
+                sk_vm_context_switch(self, self->native_switch_back_to) != 0) {
+                sk_hal_panic("switch trampoline: idle yield failed");
+            }
+            vm_frame_pop(&self->frames, idle_id); /* resumed: someone switched back in */
         }
-        self->parked_idle = 0; /* resumed: someone switched back in */
     }
 }