fix: stamp source builds above every intra-family dep floor

[Jammy2211]

Part of the fix for PyAutoLabs/PyAutoNerves#146 — main is broken: every
workspace smoke job has died at the install step since 18:08Z on 2026-08-03.

The defect

setup.py fell back to "1.0.dev0" whenever VERSION is unset — which is what
any source install does. 1.0.dev0 sorts below every date release, so a
local checkout advertised itself as older than a 2022 wheel.

That was harmless only while nothing in the family constrained a sibling. Once
the >=2026.7.29.2 floors landed (PyAutoLens#687), 1.0.dev0 could not satisfy
them and pip raised ResolutionImpossible.

Not fallout from the floors

The same defect was already biting, silently. autolens_workspace_test,
autogalaxy_workspace_test and autocti_workspace_test each carry
pip install --force-reinstall --no-deps ./PyAutoNerves, commented "the
[optional] re-resolution above can upgrade autonerves to the stale PyPI
release" — a PyPI wheel quietly shadowing the local build, patched per repo.
The floors converted a silent misinstall into a loud one, everywhere at
once.

Why 9999.0.0.dev0

• Sorts above every date release, so it satisfies present and future floors.
• Keeps .dev, so nothing ever claims the checkout is a release.
• Not read by the autonerves workspace handshake — that reads __version__
  (2026.7.23.1 on main), not pip metadata. No runtime behaviour changes.
• Release builds always export VERSION explicitly, so this default is never
  published. PyAutoHands gains a guard that fails the build if VERSION is
  empty, belt-and-braces.

Verified

• pip install ./PyAutoNerves ./PyAutoFit on main → the exact
  ResolutionImpossible seen in CI.
• The same command against these branches, with no VERSION set → resolves;
  every package installs from source at 9999.0.0.dev0, no family wheels from
  PyPI. Confirmed for both the autolens chain (5 packages) and the autocti chain.
• End-to-end pre-merge verification: DO NOT MERGE — verification harness for PyAutoNerves#146 autolens_workspace_test#246.

Merge order

All six library PRs merge together. The floors stay exactly as they are.