build(pytest): Register benchmark marker in pytest config

Add 'benchmark' marker to pytest configuration to eliminate warnings
when running control mode benchmark tests.

Marker: benchmark - Performance benchmark tests
Location: tests/control_mode/test_benchmarks.py

Author: tony

pyproject.toml

@@ -227,6 +227,9 @@ testpaths = [
   "docs",
   "README.md",
 ]
+markers = [
+  "benchmark: Performance benchmark tests",
+]
 filterwarnings = [
   "ignore:The frontend.Option(Parser)? class.*:DeprecationWarning::",
   "ignore::DeprecationWarning:libtmux.*:",