build: floor autonerves at 2026.8.23.1 for the SMALLDAT regime stamp

[Jammy2211]

Bumps autoarray's floor from autonerves>=2026.8.22.1 to >=2026.8.23.1.

Why

2026.8.22.1 was the newest release on PyPI but predates the SMALLDAT regime stamp (PyAutoNerves#153/#154). A PyPI-installed autoarray resolved an autonerves whose FITS writer emits no card at all, so should_simulate read the regime as "unknown" and fell back to the shape heuristic — which cannot see capped interferometer datasets, the case the stamp exists for.

Nothing was broken by that; it is the designed degradation. But the stamp was inert for anyone installing rather than running from a checkout. 2026.8.23.1 (nerves 0ecefa0) is the first release carrying it.

Verification

Checked against the published wheel in a clean venv with PYTHONPATH stripped, not the source tree:

autonerves 2026.8.23.1 (site-packages, no source leak)
PYAUTO_SMALL_DATASETS=1 -> SMALLDAT = True   (type: bool)
PYAUTO_SMALL_DATASETS=0 -> SMALLDAT = False  (type: bool)
keyword length <= 8: True

A genuine FITS boolean, not a string — bool("F") is True in Python, so a coerced string card would invert the regime.

Deliberately unchanged

• The shape fallback in should_simulate, and _is_capped_at_the_current_cap on the capped branch. The floor governs what a fresh install writes; it says nothing about datasets already on disk, every one of which is unstamped. Those fallbacks protect them.
• The PyAutoLens#687/#702 comment. That explains a different historical reason for this floor (JAX moving into autonerves' base deps). Both reasons are load-bearing, so the stamp reason was added, not substituted — and the comment now says so explicitly.
• The duplicated "SMALLDAT" literal in dataset_util. Importing it from autonerves becomes safe now the floor names a stamped release, but the duplication is documented and a stale reader degrades to the fallback, which is the safe direction. Converting it is optional and low value.

Closes the follow-up filed as PyAutoMind/draft/maintenance/libraries/bump_autoarray_autonerves_floor_after_stamp_release.md.