test(issue31): keep every claude tmp root candidate inside the test

The adapter's fixed /tmp fallback is now a module constant. The new tests
point it, TMPDIR, TMP and TEMP at the test's own dirs, in the test process
and (through a sitecustomize on PYTHONPATH) in every python a test starts,
so no test lists the real /tmp/claude-<uid> any more (Mac review, PR #59).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tests/test_issue31_purge_residual.py

@@ -47,6 +47,29 @@ def _fresh_id() -> str:
     return ident
 
 
+@pytest.fixture(autouse=True)
+def own_tmp_roots(tmp_path, monkeypatch):
+    """Every tmp root the claude adapter may look in stays inside the test:
+    TMP/TEMP/TMPDIR and the fixed /tmp fallback, here and in every python a
+    test starts (a sitecustomize on PYTHONPATH sets the fallback there)."""
+    from lib_py.agents.adapters import claude as claude_mod
+    sys_tmp, tmpdir, shim = tmp_path / "systmp", tmp_path / "tmpdir", tmp_path / "pyshim"
+    for d in (sys_tmp, tmpdir, shim):
+        d.mkdir()
+    monkeypatch.setattr(claude_mod, "_SYSTEM_TMP", str(sys_tmp))
+    monkeypatch.setenv("TMPDIR", str(tmpdir))
+    monkeypatch.delenv("TMP", raising=False)
+    monkeypatch.delenv("TEMP", raising=False)
+    (shim / "sitecustomize.py").write_text(
+        "try:\n"
+        "    from lib_py.agents.adapters import claude\n"
+        f"    claude._SYSTEM_TMP = {str(sys_tmp)!r}\n"
+        "except Exception:\n"
+        "    pass\n")
+    monkeypatch.setenv("PYTHONPATH", f"{shim}:{os.environ.get('PYTHONPATH', '')}")
+    return sys_tmp
+
+
 @pytest.fixture
 def conv() -> str:
     return _fresh_id()
@@ -411,14 +434,14 @@ def test_a_job_dir_that_cannot_be_emptied_keeps_its_state_json(home, tmp_path, m
     assert adapter.residual_artifacts(conv, ctx) == []
 
 
-def test_claude_tmp_root_rules(tmp_path, monkeypatch):
+def test_claude_tmp_root_rules(tmp_path, monkeypatch, own_tmp_roots):
     from lib_py.agents.adapters.claude import _tmp_roots
     name = f"claude-{UID}"
     x, y, z = tmp_path / "x", tmp_path / "y", tmp_path / "z"
-    for d in (x / name, y / name, z / name):
+    for d in (x / name, y / name, z / name, own_tmp_roots / name):
         d.mkdir(parents=True)
     real = lambda roots: [os.path.realpath(r) for r in roots]  # noqa: E731
-    sys_tmp = [os.path.realpath(f"/tmp/{name}")] if os.path.isdir(f"/tmp/{name}") else []
+    sys_tmp = [os.path.realpath(str(own_tmp_roots / name))]
 
     monkeypatch.setenv("CLAUDE_CODE_TMPDIR", str(x))
     monkeypatch.setenv("TMPDIR", str(z) + "/")
@@ -438,6 +461,14 @@ def test_claude_tmp_root_rules(tmp_path, monkeypatch):
     assert real(_tmp_roots()) == [str(z / name)] + sys_tmp
 
 
+def test_tests_never_reach_the_real_tmp_root(tmp_path, own_tmp_roots):
+    from lib_py.agents.adapters.claude import _tmp_roots
+    assert all(os.path.realpath(r).startswith(os.path.realpath(str(tmp_path))) for r in _tmp_roots())
+    res = subprocess.run([sys.executable, "-c", "from lib_py.agents.adapters import claude; print(claude._SYSTEM_TMP)"],
+                         capture_output=True, text=True, env=_env(), timeout=30)
+    assert res.stdout.strip() == str(own_tmp_roots), res.stdout + res.stderr
+
+
 # ---------------------------------------------------------------------------
 # in-use CLI and the stop gate
 # ---------------------------------------------------------------------------