test: isolate pytest runtime defaults across workers and runs

tests/test_research_report_read.py

@@ -14,21 +14,20 @@ These tests pin both halves:
    web_fetching the HTML report.
 """
 import json
-from pathlib import Path
 
 import pytest
 
 from src.tool_implementations import do_manage_research
 from src.agent_loop import TOOL_SECTIONS
 
-_DATA_DIR = Path("data/deep_research")
-
 
 @pytest.fixture
-def saved_report():
-    _DATA_DIR.mkdir(parents=True, exist_ok=True)
+def saved_report(tmp_path, monkeypatch):
+    from src.tools import research
+
+    monkeypatch.setattr(research, "DEEP_RESEARCH_DIR", str(tmp_path))
     rid = "rp-testreport1363"
-    path = _DATA_DIR / f"{rid}.json"
+    path = tmp_path / f"{rid}.json"
     path.write_text(json.dumps({
         "query": "trending blender video ideas",
         "result": "## Findings\nShort-form Geometry Nodes tutorials are trending.",