test: add -> None return type annotations to all test methods

shellhist/tests/test_time.py

@@ -10,7 +10,7 @@ from shellhist.core import HistoryEntry, HistoryStore
 class TestTimeUtils:
     """Test time utility functions."""
 
-    def test_parse_time_range_hours(self):
+    def test_parse_time_range_hours(self) -> None:
         """Test parsing hour-based time range."""
         from shellhist.cli.time_analysis import _parse_time_range
         
@@ -19,7 +19,7 @@ class TestTimeUtils:
         
         assert (result - expected).total_seconds() < 5
 
-    def test_parse_time_range_days(self):
+    def test_parse_time_range_days(self) -> None:
         """Test parsing day-based time range."""
         from shellhist.cli.time_analysis import _parse_time_range
         
@@ -28,7 +28,7 @@ class TestTimeUtils:
         
         assert (result - expected).total_seconds() < 5
 
-    def test_parse_time_range_weeks(self):
+    def test_parse_time_range_weeks(self) -> None:
         """Test parsing week-based time range."""
         from shellhist.cli.time_analysis import _parse_time_range
         
@@ -41,7 +41,7 @@ class TestTimeUtils:
 class TestHourlyDistribution:
     """Test hourly distribution analysis."""
 
-    def test_hourly_analysis(self):
+    def test_hourly_analysis(self) -> None:
         """Test basic hourly distribution."""
         from shellhist.cli.time_analysis import _analyze_hourly_distribution
         from rich.console import Console