test: pin interpreter probe so py-template render test passes on Windows (#3428)

test_template_renders_python_invocation monkeypatches shutil.which to
return /usr/bin/python3, but on Windows resolve_python_interpreter guards
the which() result with a real _interpreter_runs subprocess probe (#3304).
The mocked /usr/bin/python3 path does not exist on a Windows runner, so the
probe fails, the resolver falls back to sys.executable (a ...python.exe
path), and the python3-anchored regex assertion fails.

Patch _interpreter_runs to return True in the _pin_interpreter fixture so
the resolved interpreter token stays python3 across all platforms, keeping
the #3304 production guard intact while making the assertion deterministic.

Assisted-by: GitHub Copilot (model: Claude Opus 4.8, autonomous)

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

tests/test_command_template_py_scripts.py

@@ -39,6 +39,17 @@ def _pin_interpreter(monkeypatch):
         "specify_cli.integrations.base.shutil.which",
         lambda name: "/usr/bin/python3" if name == "python3" else None,
     )
+    # On Windows, ``resolve_python_interpreter`` guards the ``which`` result
+    # with a real ``_interpreter_runs`` subprocess probe (#3304). The mocked
+    # ``/usr/bin/python3`` path does not exist on a Windows runner, so the
+    # probe would fail and the resolver would fall back to ``sys.executable``
+    # (a ``...python.exe`` path), breaking the ``python3``-anchored assertion.
+    # Pin the probe to True so the interpreter token stays ``python3`` on all
+    # platforms.
+    monkeypatch.setattr(
+        "specify_cli.integrations.base.IntegrationBase._interpreter_runs",
+        staticmethod(lambda path: True),
+    )
 
 
 def test_py_templates_discovered():