fix: ruff findings

tests/test_repair.py

@@ -4,9 +4,8 @@ Tests the idempotent, safe repair of hour observations and day aggregates
 from surviving raw samples, boundary anchor retention, and legacy summary
 handling at actual precision.
 """
-import sqlite3
 import sys
-from datetime import datetime, timedelta, timezone
+from datetime import datetime, timezone
 from pathlib import Path
 
 import pytest
@@ -102,7 +101,6 @@ class TestRepairUsesSameEvidenceRules:
 
     def test_repair_idempotent_on_fully_derived(self, store_conn):
         """Repair on store with existing derived data does not duplicate."""
-        now = datetime(2026, 9, 15, 12, 0, 0, tzinfo=timezone.utc)
         _open_period(store_conn, "2026-09-14T00:00:00+00:00")
         
         # Insert samples that span an hour
@@ -138,7 +136,7 @@ class TestRepairUsesSameEvidenceRules:
         store_conn.commit()
         
         # Run repair
-        result = repair_derivation(store_conn)
+        repair_derivation(store_conn)
         
         # Verify marker preserved
         cursor = store_conn.execute(
@@ -265,7 +263,7 @@ class TestBoundaryAnchorRetention:
         _insert_sample(store_conn, "2026-09-29T12:00:00+00:00", 3000000)
         
         # Run pruning
-        pruned = prune_old_samples(store_conn, now, retention_days=14)
+        prune_old_samples(store_conn, now, retention_days=14)
         
         # The boundary anchor should be retained
         cursor = store_conn.execute(
@@ -286,7 +284,7 @@ class TestBoundaryAnchorRetention:
                      bytes_written_delta=1000000)
         
         # Run pruning
-        pruned = prune_old_samples(store_conn, now, retention_days=14)
+        prune_old_samples(store_conn, now, retention_days=14)
         
         # The source remains until local-day evidence is also durable.
         cursor = store_conn.execute(
@@ -309,7 +307,7 @@ class TestLegacySummaryPrecision:
                              bytes_written_delta=5000000)
         
         # Run repair
-        result = repair_derivation(store_conn)
+        repair_derivation(store_conn)
         
         # Should not create hour observations for legacy day
         cursor = store_conn.execute(
@@ -324,7 +322,7 @@ class TestLegacySummaryPrecision:
                              bytes_written_delta=5000000)
         
         # Run repair
-        result = repair_derivation(store_conn)
+        repair_derivation(store_conn)
         
         # Day aggregate should not be modified
         cursor = store_conn.execute(