test: keep the CLI's saved selections out of the user's home (#1395)

- every test saves and reads CLI selections under its own tmp_path

tests/test_suite_isolation.py

@@ -1,4 +1,4 @@
-"""The suite runs the same on any machine: no test reaches the network."""
+"""The suite runs the same on any machine: no test reaches the network or the user's files."""
 
 import socket
 
@@ -15,3 +15,15 @@ def test_a_test_cannot_reach_the_network(connect):
     machine it runs on; conftest refuses the connection instead."""
     with pytest.raises(OSError, match="reach the network"):
         connect()
+
+
+@pytest.mark.unit
+def test_a_test_saves_cli_selections_to_its_own_directory(tmp_path):
+    """The CLI remembers the last run's selections in the user's home; a test
+    that runs the selection flow would otherwise overwrite them."""
+    from cli import prefs
+
+    prefs.save_last_run({"analysts": ["market"]})
+
+    assert prefs._PREFS_PATH.is_relative_to(tmp_path)
+    assert prefs._PREFS_PATH.exists()