feat: add unity_testing_run_tests, get_job, list_tests tools

Async job-based test runner integration with Unity Test Runner API.
- unity_testing_run_tests: start test runs with filters (mode, names,
  categories, assemblies), auto-polls for 2s initial feedback
- unity_testing_get_job: poll progress/results with server-side wait
  (waitTimeout) to reduce client round-trips
- unity_testing_list_tests: discover available tests by mode

All three added to CORE_TOOLS tier. Bridge functions added for
testing/run-tests, testing/get-job, testing/list-tests routes.