Move HAETAE OID arc from bc-sig.16 to bc-sig.18

bc-sig.16 collides with the QR-UOV branch (pqc-qruov), which also
claims that arc on its own pending merge. To avoid the silent
"duplicate provider key (Alg.Alias.KeyFactory.<oid>)" failure CLAUDE.md
warns about when two PQC algorithms claim the same parent arc, HAETAE
moves to the next free slot above the AIMer assignment at bc-sig.17.

Updated arcs across main and pending branches:
  bc-sig.13 = mqom  (in main)
  bc-sig.14 = uov   (in main)
  bc-sig.15 = hawk  (in main)
  bc-sig.16 = qruov (pending, pqc-qruov)
  bc-sig.17 = aimer (pending, kpqc-aimer)
  bc-sig.18 = haetae (this commit)

The release note's BC-arc citation now reads "haetae.{1..3} under
bc-sig.18" so the parent arc is discoverable from the release notes,
matching the citation style established by the Hawk, QR-UOV and AIMer
notes.