docs(should_simulate): the point-source "not in this gap" note is repo-specific (#480)

The Known-gap section stated that point-source datasets "are not in this gap:
they write a top-level `data.fits` alongside their JSON and are covered
normally". That holds in autolens_workspace. It is false in
autolens_workspace_test, whose `.gitignore` lists `data.fits` under "Generated
artifacts — never check in", so `dataset/point_source/simple` is three tracked
JSON files and nothing else — no `SMALLDAT` stamp can exist there under any
placement.

That is precisely the directory PyAutoArray#470 was about, so the paragraph
reassured the reader about the one case that bit us: the capped branch deleted
that committed, allowlist-protected directory on every smoke run.

Whether a dataset family is reachable by the stamp is decided per repository by
that repo's `.gitignore`, never by the family name. Says so, and points at the
PyAutoHands guard (PyAutoHands#252) that enforces what a docstring cannot.

Docstring only — no behaviour change.

Refs #470


Claude-Session: https://claude.ai/code/session_01F11sMzmaVWfU6NCz1PKVVb

Co-authored-by: Jammy2211 <JNightingale2211@gmail.com>
Co-authored-by: Claude Opus 5 <noreply@anthropic.com>

Author: 3 people

autoarray/util/dataset_util.py

@@ -354,10 +354,28 @@ def should_simulate(dataset_path):
     the reach of a destructive predicate is its own change, with its own review,
     not a rider on the one that changes where its input comes from.
 
-    Note that point-source datasets are **not** in this gap: they write a
-    top-level ``data.fits`` alongside their JSON and are covered normally. The
-    original issue text grouped them with weak lensing as "JSON with no FITS";
-    that is true of weak lensing only.
+    Note that point-source datasets are **not** in this gap *in
+    ``autolens_workspace``*: there they write a top-level ``data.fits`` alongside
+    their JSON and are covered normally. The original issue text grouped them
+    with weak lensing as "JSON with no FITS"; that is true of weak lensing only
+    in that repo.
+
+    It is **not** true everywhere, and the exception is not hypothetical.
+    Whether a dataset family is reachable by the stamp is decided per repository
+    by that repo's ``.gitignore``, never by the family name.
+    ``autolens_workspace_test`` lists ``data.fits`` under "Generated artifacts —
+    never check in", so its ``dataset/point_source/simple`` is three tracked JSON
+    files and nothing else -- no stamp can exist there under any placement, and
+    the capped branch deleted that committed, allowlist-protected directory on
+    every smoke run (PyAutoArray#470, fixed workspace-side in
+    autolens_workspace_test#264).
+
+    So do not read this paragraph as "point-source is safe". Read it as "point
+    source is safe wherever a top-level ``data.fits`` is actually written".
+    ``PyAutoHands``' ``check_dataset_allowlist`` guard now fails a ``pre_build``
+    run when a ``should_simulate`` call site that has not released
+    ``PYAUTO_SMALL_DATASETS`` would delete git-tracked files, which is the
+    check this docstring cannot itself enforce.
     """
     if os.environ.get("PYAUTO_SMALL_DATASETS") == "1":
         if Path(dataset_path).exists() and not _is_capped_at_the_current_cap(