Why: C4 and C5 need a shared way to start, refuse, and tear down stacks without touching production ports or processes.
Evidence: tests/ops/self_check.sh passed (help, unknown arg, foreign name, production port, busy port, SIGINT cleanup). drill_driver go test passed.
Impact: New tests/ops library and HTTP driver. No drill result and no release-gate change yet.
Refs: docs/release-multi-instance.md C4 C5
Co-authored-by: Cursor <cursoragent@cursor.com>
