Fix `required_passes` docs and (implementation for large results)

The new direct positive-path Hypothesis-based test wants to pass in huge
numbers and the float-based implementation does not do well for these inputs.
Happily, we can do better.

Only the documentation was wrong, whew.

Add behavior to the client to automatically maintain leases

Add Python runtime requirements to setup.cfg

not the time itself

/calling/ *bracket* performs the operation