fix: ruff findings

tests/test_collector_tracer.py

@@ -6,13 +6,11 @@ Tests the thinnest complete write path through the system:
 
 Seam: write side of the observation store database file.
 """
-import json
 import os
 import sqlite3
-import tempfile
 from datetime import datetime, timezone
 from pathlib import Path
-from typing import Any, Dict, Generator
+from typing import Any, Dict
 
 import pytest
 
@@ -20,8 +18,8 @@ import pytest
 import sys
 sys.path.insert(0, str(Path(__file__).parent.parent / "src"))
 
-from fenris.collector import run_collection, AcquisitionError, InvariantViolationError
-from fenris.store import init_store, get_store_path
+from fenris.collector import run_collection
+from fenris.store import init_store
 
 
 # Fixtures