fix(ci): pytest 'import file mismatch' collection errors on test branch

[aix-ahmet]

CI on the test branch (and any branch running the full suite) aborts collection with 6 import file mismatch errors:

imported module 'test_model' has this __file__ attribute:
  .../tests/functional/v2/test_model.py
which is not the same as the test file we want to collect:
  .../tests/unit/v2/test_model.py

Root cause: duplicate test basenames (test_model.py, test_tool.py, test_session.py, test_trigger.py, test_api_key.py, test_rlm.py) across tests/unit/v2, tests/functional/v2, and tests/functional/model. Most test dirs have no __init__.py, so pytest's default prepend import mode assigns both files the same top-level module name and aborts.

Fix: addopts = --import-mode=importlib in pytest.ini — each test file gets a fully-qualified module name, so unique basenames are no longer required. This is pytest's recommended mode for new projects.

Verification:

• pytest --collect-only: 1808 tests collected, 0 errors (was 1458 + 6 errors, collection interrupted)
• pytest tests/unit: 1388 passed, 4 skipped
• No test module imports another test module by bare name (the one pattern importlib mode would break)

🤖 Generated with Claude Code

https://claude.ai/code/session_018dCb6BE5bqjCrmsiPDGLRr