§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>

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