fix: ruff findings

tests/test_complete_observation_day_gate.py

@@ -13,7 +13,6 @@ Acceptance criteria:
 - Gate-3: Partial days don't satisfy the gate
 - Gate-4: CLI and TUI share the same gate via compute_projection()
 """
-import sqlite3
 from datetime import datetime, timedelta, timezone
 from pathlib import Path
 
@@ -24,8 +23,7 @@ sys.path.insert(0, str(Path(__file__).parent.parent / "src"))
 from fenris.store import init_store
 from fenris.monitoring_periods import ensure_period_open
 from fenris.projection import (
-    compute_projection, ConfidenceState, BaselineTier,
-    WARMING_COVERAGE_FLOOR,
+    compute_projection, ConfidenceState,
 )