make quality runs mypy over tests/ too; the toolchain test fixtures
(monkeypatch params, the fake-subprocess factories) were missing annotations.
No behavior change.
Adds _toolchain_broken_guard: when toolchain matching is on and the acting
agent's workspace recorded a 'broken' status (the project's suite cannot be
collected under the provisioned interpreter), i_am_done, pass_review, and
pr_pass refuse with an i_am_blocked remediation instead of letting the role
"pass" on a source read. fail_review / pr_fail stay available. git gains
toolchain_status_for_task (resolves the actor's workspace, reads the marker,
fail-open None). Inert when the flag is off; a missing/unknown status never
strands a task.
Renn F