§H.12 steps 7-9: thread real parent VMUuid through the birth call chain

Session.parent now comes from the actual birthing VM's own
stadium_vm_id, not a hardcoded vm_uuid_hera(). Added a VMUuid parent
parameter to capsule_birth_baby() and, one level up, to
capsule_console_birth()/capsule_runcap_birth() (neither had a VM* in
their own signature, but every caller did). Updated all 6 real call
sites: BIRTH, CAPSULE-BIRTH, CONNECT-ARTEMIS, CONNECT-HERMES,
RUNCAP-TEST, PAIR-TEST (mama_forth_words.c) and the console+user birth
pair in capsule_wirebind_try_attach() (capsule_wirebind.c). Two
functions had their vm parameter marked __attribute__((unused)), now
genuinely used -- attribute removed.

Steps 8 (Session.name from capsule name) and 9 (identity defaults to
installed=0) were already satisfied by step 5's existing
session_register() call and its identity-zeroing -- confirmed by
inspection, no further code needed.

Verified 3-arch boot to ok> (amd64/aarch64/riscv64).

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

include/starkernel/capsule_birth.h

@@ -127,6 +127,14 @@ CapsuleRunResult capsule_birth_mama(
  * @param descs         Capsule descriptor array
  * @param names         Capsule name entry array (parallel to descs)
  * @param arena         Capsule payload arena
+ * @param parent        Who is birthing this VM (FABRIC-3.md §H.12 step 7) --
+ *                       the caller's own VMUuid (e.g. vm->stadium_vm_id for
+ *                       a FORTH word handler), recorded on the new VM's
+ *                       Session.parent. Every current call site has one in
+ *                       scope, directly or one level up; traced live rather
+ *                       than assumed (checked all 6 call sites across
+ *                       mama_forth_words.c/capsule_console.c/
+ *                       capsule_runcap.c/capsule_wirebind.c).
  * @param skip_pki_sig  0 for every build-time capsule (the normal case --
  *                       checked against the compile-time-baked signature
  *                       array via capsule_get_signatures()). Non-zero only
@@ -154,6 +162,7 @@ CapsuleRunResult capsule_birth_baby(
     const CapsuleDesc *descs,
     const CapsuleNameEntry *names,
     const uint8_t *arena,
+    VMUuid parent,
     int skip_pki_sig,
     VMUuid *out_vm_id,
     void **out_vm_ctx