[Jammy2211]

Summary

import autocti now works on a machine without arcticpy installed. arcticpy has no PyPI wheel; building it needs GSL and a C++ compiler, so docs builds, PyAutoEyes, the assistant and new users all used to fail at the import, even when they never clock any charge. Datasets, layouts, masks, plotting and loading results now work without it. Only clocking, and the arcticpy classes autocti re-exports, need it, and they say so with an error that names the install recipe.

Closes #117 (cti-upkeep phase 2c, ruling R2).

• autocti/_arcticpy.py (new):
  • arcticpy() imports the module, or raises ImportError with the recipe (PyAutoHeart install_arcticpy.sh).
  • optional_import(*names) returns the real objects, or, without arcticpy, placeholders that raise that error when called.
  • The placeholders are real classes, so PyAutoFit can still evaluate constructor type hints such as Optional[List[TrapInstantCapture]]. A TYPE_CHECKING approach broke af.Model and was dropped.
• autocti/__init__.py: the nine re-exports resolve on first use through a PEP 562 __getattr__ / __dir__.
• clocker/, model/model_util.py, model/settings.py, charge_injection/ou_sim_ci.py: use optional_import instead of from arcticpy import ....

API Changes

No change for anyone with arcticpy installed: every name (ac.TrapInstantCapture, from autocti import CCDPhase, ac.ROE, ...) is the identical arcticpy object, and a test asserts this.
Without arcticpy: import autocti succeeds. Using a re-exported arcticpy name, building a clocker, or clocking raises ImportError with the install recipe. Before this change, import autocti itself failed with ModuleNotFoundError: arcticpy.

Tests

• New test_autocti/test_lazy_arcticpy.py hides arcticpy in a subprocess (sys.modules['arcticpy'] = None). It checks that import autocti works, that a re-exported name and Clocker1D raise the recipe error, and that with arcticpy installed the re-exports are the same objects. Control: all 4 fail on unchanged main.
• Full test_autocti: 275 passed when run serially. Under -n 8, the 5 instruments/acs/test_image.py tests collide on shared FITS output files; they pass serially, both here and on main.
• autocti_workspace_test scripts/{dataset_1d,imaging_ci}/likelihood/pins.py: OK. All 10 likelihood literals still match at rtol 1e-8.
• autocti_workspace smoke (3 scripts, profile_smoke): 3/3 pass.
• Downstream: no code in autocti_visualization or autocti_assistant imports arcticpy names.

Heart readiness at ship time: STALE (85). The one reason is that release validation is out of date after PyAutoNerves#210 merged, which concerns the next release only, not this feature.

Tier: judge, merge mode: human /prm.

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