Skip CLI tests when click is not installed

Uses pytest.importorskip so test collection succeeds in CI
environments that don't install the cli extra.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: waltsims

tests/test_cli/conftest.py

@@ -3,9 +3,11 @@
 import json
 
 import pytest
-from click.testing import CliRunner
 
-from kwave.cli.main import cli
+click = pytest.importorskip("click", reason="CLI tests require click: pip install k-wave-python[cli]")
+from click.testing import CliRunner  # noqa: E402
+
+from kwave.cli.main import cli  # noqa: E402
 
 
 def invoke(runner, args, session_dir):