Summary

• Avoid default process-pool fork when the parent process already has multiple threads, using forkserver/spawn where available.
• Make the heartbeat active-function test deterministic by blocking slow_square until observed.
• Reuse the safe process-pool factory in the memory-storage parallel test.

Test Plan

• uv run pytest tests/test_run_status_cli.py::test_status_from_run_folder_uses_heartbeat_by_default
• uv run pytest tests/map/test_map.py::test_default_process_pool_executor_avoids_fork_when_threads_exist
• uv run pytest 'tests/map/test_map.py::test_parallel_memory_storage[dict]'\n- uvx nox -e pytest_min_deps-3.13 -v\n- uvx nox -e pytest_all_deps-3.12 -v\n- uv run pre-commit run --all-files