test(confinement): give user-content carve-out cases stable ids (#6555)

test_allows_user_content_the_app_hands_to_the_model is parametrized on
UPLOAD_DIR and friends, which sit under the per-worker data dir. pytest
used those paths as test ids, so every xdist worker collected different
names and `pytest -n 4` (documented in tests/README.md) aborted at
collection. CI shards with --shard and never saw it.

tests/test_agent_state_dir_confinement.py

@@ -331,7 +331,9 @@ def test_allows_files_in_the_agent_workspace():
     (PERSONAL_UPLOADS_DIR,
      "indexed into personal docs by routes/personal_routes.py, and listed as "
      "an absolute path by manage_rag"),
-])
+# The directories live under a per-worker data dir, so they cannot be test ids:
+# xdist requires every worker to collect the same names.
+], ids=["uploads", "mail_attachments", "personal", "personal_uploads"])
 def test_allows_user_content_the_app_hands_to_the_model(directory, why):
     """Carving these out is not convenience. The app gives the model these
     paths and tells it to read them, so denying them breaks the feature."""