fix(v4): a killed node's children become Hera's; Review Focus 4 checked

From the final review of MESH step 7.  NODE-KILL left children whose parent
was the dead number, so a node born later under it inherited authority over
them; they are re-parented to Hera.  After UNIT-KILL Hera no longer lists the
removed centre, and a later KILL completes (shown to fail with GONE-DOWN's
unlisting taken out).  test_manage 45/45 both widths; test_host_unit 127/127.

Acceptance: amd64, aarch64, riscv64 clean qemu: ok>, POST 538/538,
dict_hash=0x248b4edc47f4357e on all three; test-32 0 failures.

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

v4/include/v4/manage.h

@@ -25,7 +25,8 @@
  *   -11 NODE-WAKE    ( number -- )             Hera
  *   -12 NODE-KILL    ( number -- )             Hera; not herself; a number not
  *                                              live does nothing.  The node's
- *                                              children are not removed, as v3.
+ *                                              children are not removed, as v3,
+ *                                              and become Hera's children.
  *   -13 NODE-PARITY  ( place number -- )       for a node the asker birthed,
  *                                              under the number it was born as
  *   -14 CAPSULE-OPEN ( baddr u -- flag )       any node in the registry: the