test(audit_heuristics): add 3 regression tests for lazy-loading (Phase 12)

Three regression-guard tests in tests/test_audit_heuristics.py verify
the new lazy-loading sentinel fallback heuristic (commit f996aa10):

- test_lazy_loading_sentinel_fallback_in_resolve_is_compliant:
  L65-style nested try/except with self._cached = _FiledialogStub()
  in _resolve (mirrors the actual site in src/gui_2.py:65)
  -> expects INTERNAL_COMPLIANT
- test_lazy_loading_sentinel_fallback_in_load_is_compliant:
  direct self._cached = _FooStub() in _load
  -> expects INTERNAL_COMPLIANT
- test_lazy_loading_sentinel_fallback_in_get_is_compliant:
  direct self._cached = _BarStub() in _get (catches AttributeError
  after a getattr call)
  -> expects INTERNAL_COMPLIANT

These tests follow the existing _make_visitor / _find_handler pattern
established by Phase 7 (BOUNDARY_FASTAPI) and Phase 11 (dunder-method
bare-raise) tests. They lock the heuristic's behavior so future edits
to scripts/audit_exception_handling.py cannot accidentally reclassify
the 2 gui_2.py sites (L65, L69) back to UNCLEAR.

Pre-Phase 12: 3 tests in this file (Phase 7 + Phase 11).
Post-Phase 12: 6 tests. 13/13 tests pass (3 new + 10 existing).

Phase 12 result_migration_gui_2_20260619.

tests/test_audit_heuristics.py

@@ -221,3 +221,78 @@ def test_bare_raise_in_getattribute_is_programmer_raise():
   f"should be INTERNAL_PROGRAMMER_RAISE (canonical dunder-method pattern); "
   f"got {category}. Hint: {hint}"
  )
+
+
+# Phase 12 Task 12.1 - Regression-guard tests for the lazy-loading sentinel
+# fallback heuristic.
+# Per Phase 12 spec (INTERNAL_COMPLIANT classification for lazy-loading
+# sentinel fallbacks in methods named _resolve/_load/_get/_try_load):
+# - The except body must NOT re-raise
+# - The except body must assign to a self.<attr> (directly or via nested try)
+# - The except set must be in {AttributeError, ImportError, ModuleNotFoundError}
+# - The enclosing function name must be in the lazy-loader set
+# Pre-Phase 12 baseline: 2 UNCLEAR sites in src/gui_2.py at L65, L69
+# (both in _LazyModule._resolve). Post-Phase 12: 0 UNCLEAR.
+
+def test_lazy_loading_sentinel_fallback_in_resolve_is_compliant():
+ src = (
+  "def _resolve(self):\n"
+  " try:\n"
+  "  self._cached = getattr(self._mod, self._attr_name)\n"
+  " except AttributeError:\n"
+  "  try:\n"
+  "   self._cached = _importlib.import_module(self._sub_name)\n"
+  "  except (ImportError, ModuleNotFoundError):\n"
+  "   self._cached = _FiledialogStub()\n"
+  " return self._cached\n"
+ )
+ visitor = _make_visitor(src, "_resolve")
+ try_node = _find_handler(visitor)
+ handler = try_node.handlers[0]
+ category, hint = visitor._classify_except(handler, try_node)
+ assert category == "INTERNAL_COMPLIANT", (
+  f"Phase 12 regression: lazy-loading sentinel fallback in `_resolve` "
+  f"(L65-style nested try with `self._cached = _FiledialogStub()`) "
+  f"should be INTERNAL_COMPLIANT (canonical graceful-degradation pattern); "
+  f"got {category}. Hint: {hint}"
+ )
+
+
+def test_lazy_loading_sentinel_fallback_in_load_is_compliant():
+ src = (
+  "def _load(self, name):\n"
+  " try:\n"
+  "  self._cached = _importlib.import_module(name)\n"
+  " except (ImportError, ModuleNotFoundError):\n"
+  "  self._cached = _FooStub()\n"
+  " return self._cached\n"
+ )
+ visitor = _make_visitor(src, "_load")
+ try_node = _find_handler(visitor)
+ handler = try_node.handlers[0]
+ category, hint = visitor._classify_except(handler, try_node)
+ assert category == "INTERNAL_COMPLIANT", (
+  f"Phase 12 regression: lazy-loading sentinel fallback in `_load` "
+  f"(direct `self._cached = _FooStub()`) should be INTERNAL_COMPLIANT "
+  f"(canonical graceful-degradation pattern); got {category}. Hint: {hint}"
+ )
+
+
+def test_lazy_loading_sentinel_fallback_in_get_is_compliant():
+ src = (
+  "def _get(self, attr_name):\n"
+  " try:\n"
+  "  return getattr(self._module, attr_name)\n"
+  " except AttributeError:\n"
+  "  self._cached = _BarStub()\n"
+  "  return self._cached\n"
+ )
+ visitor = _make_visitor(src, "_get")
+ try_node = _find_handler(visitor)
+ handler = try_node.handlers[0]
+ category, hint = visitor._classify_except(handler, try_node)
+ assert category == "INTERNAL_COMPLIANT", (
+  f"Phase 12 regression: lazy-loading sentinel fallback in `_get` "
+  f"(direct `self._cached = _BarStub()`) should be INTERNAL_COMPLIANT "
+  f"(canonical graceful-degradation pattern); got {category}. Hint: {hint}"
+ )