/pygienium-todos inventories TODO/FIXME/HACK markers and stub bodies via a
deterministic pre-scan plus the todos sub-agent; --fix converts silent
stubs (placeholder returns, empty/pass bodies) into loud failures,
never implementing TODOs or deleting markers. Replaces the noop
reference check; the extensibility suite now registers a synthetic
witness. Adds agents/todos.md and tests/todos.test.ts.
