Summary

Forces ENGRAPHIS_EXTRACTOR=none in the root conftest.py instead of using setdefault, closing a leak where an owner-machine shell export (ENGRAPHIS_EXTRACTOR=llm_structured) put a live LLM extractor into the offline unit gate.

Root cause

• The offline gate contract (AGENTS.md §1) requires python -m pytest tests/ -q to pass network-free.
• conftest's previous guard used os.environ.setdefault("ENGRAPHIS_EXTRACTOR", "none"), which defers to any pre-existing shell variable.
• On machines exporting the variable, every ingest-path test constructed a real extractor; under tests/conftest.py's DNS stub the extraction call hangs rather than failing fast.
• Observed effect: deterministic timeout failure of test_session_close_linearizes_before_delayed_memory_write[ingest] — the writer thread never reached the embed hook within the test window.

Fix

• Direct assignment (os.environ["ENGRAPHIS_EXTRACTOR"] = "none"), matching the existing ENGRAPHIS_UPDATE_CHECK treatment in the same file.
• Tests that deliberately exercise extraction still opt in explicitly via monkeypatch.setenv; no test relies on shell-passthrough (verified by grep across tests/).

Verification

• Previously failing test + full file: pass.
• Full suite pytest tests/ -q distributed: green (exit 0).
• ruff clean; pyright 0 errors/0 warnings on core+backends; commercial manifest OK; asset-drift check OK.