Stage E: every born VM is a switch participant (FABRIC-3.8 §3.6, G4)

capsule_birth_baby() registers each VM at its LIVE completion point, beside
the common-channel subscription. register() is idempotent. The Artemis/
Hestia registrations in kernel_main.c and WIREBIND's own call are removed
(Hera, never born through capsule_birth_baby, stays with set_current).

Probe (restored away): Tripod registered once each (3 slots), a
WORKER-BIRTH VM becomes a participant with no hand registration (4) and
KILL frees it (3), WIREBIND registers exactly console+user, zero
duplicates, on amd64/aarch64/riscv64. Acceptance: dict_hash unchanged,
relay 3, idle growth 0.

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

include/starkernel/capsule_vm_switch_signal.h

@@ -85,7 +85,10 @@ int sk_vm_switch_signal_boot_init(void);
  * or -1 if the slot table is full (or sk_vm_switch_signal_boot_init() was
  * never called / failed). Call once per participating VM, after that VM is
  * fully born (never mid-birth -- this stage has no critical-section
- * protection against being switched away mid-setup). */
+ * protection against being switched away mid-setup). FABRIC-3.8.md §3.6
+ * (Stage E): capsule_birth_baby() is now the one caller for every born VM
+ * (Hera, never born through it, is registered in kernel_main.c).
+ * Idempotent: registering an already-registered VM returns its slot. */
 int sk_vm_switch_signal_register(VMUuid vm_id);
 
 /* Remove a switch-signal participant (FABRIC-3.md §XXVIII Stage 4,