fix timezone handling and logging fallback robustness

tests/test_logging.py

@@ -11,6 +11,7 @@ from vlm.logging_config import (
     get_logger,
     log_operation,
     MAX_LOG_SIZE,
+    default_log_dir,
 )
 
 
@@ -71,6 +72,28 @@ class TestLoggingSetup:
             logger = setup_logging(log_level=level, log_dir=tmp_path)
             assert logger is not None
 
+    def test_setup_logging_falls_back_when_file_logging_unwritable(self, tmp_path, monkeypatch):
+        """Test setup continues with console logging if file logging cannot initialize."""
+        def fail_mkdir(self, parents=False, exist_ok=False):
+            raise PermissionError("mock permission denied")
+
+        monkeypatch.setattr(Path, "mkdir", fail_mkdir)
+
+        logger = setup_logging(log_level="INFO", log_dir=tmp_path / "logs")
+
+        logger.info("Console-only logging still works")
+        assert len(logger.handlers) == 1
+        assert isinstance(logger.handlers[0], logging.StreamHandler)
+
+
+class TestDefaultPathResolution:
+    """Test runtime default path resolution."""
+
+    def test_default_log_dir_resolves_at_runtime(self, tmp_path, monkeypatch):
+        """Test default log directory follows current Path.home() value."""
+        monkeypatch.setattr(Path, "home", lambda: tmp_path)
+        assert default_log_dir() == tmp_path / ".vlm" / "logs"
+
 
 class TestDualOutput:
     """Test dual output to console and file."""