Both are DRY BY DEFAULT, IDEMPOTENT, and READ BACK every write -- this repo has
been bitten by a script whose `apply` always silently dry-ran, so a create that
reports success is re-read before being called done.

carve-v6 places each v6 plane on the SAME MAAS vlan as its v4 twin, so the plane
is genuinely dual-stack on one L2 rather than a parallel fabric, and REFUSES to
create anything if that vlan cannot be resolved. The provider GUA VIP /64 is
skipped by design.

reserve does the D-134 bands plus the FIP pool. Two deliberate refusals:
- dc1's FIP pool is UNSET in lib-net BY DESIGN ("UNSET so any use fails loud").
  Mirroring dc0's shape would be an inferred value, so it refuses and reports
  that R4 cannot be fully executed for dc1 until the pool is ruled. Real finding.
- a same-bounds range of the wrong type is REFUSED, not overwritten.
v6 bands are skipped until carve-v6 has run -- R4's forced sequencing, surfaced
rather than silently passing.

TWO BUGS CAUGHT PRE-SHIP, neither by review:
- printf '%x' 50 yields 32, so the v6 bands would have been created at ::32-::63
  -- a plausible-looking band that is NOT the one ruled. The ruling mirrors the
  DIGITS (v4 .50 -> ::50). T19 locks it.
- `shift 2` with a single argument fails, leaving "$@" holding the action, which
  the option loop rejected as an unknown option instead of printing usage. Found
  by the harness.
The header claiming the mutating actions were absent is also corrected -- it went
stale the moment they landed.

Gauntlet ALL GREEN (83), repo-lint 0 fail.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01HvCyrwvYTTcDYnRErfMsNf