Allow users to change document properties and re-run automatic steps

Sometimes you want to change the document settings (language, number of speakers) and then rerun the tasks that depend on it

The issue names no files, tests, or entry points. Begin by locating where document language and speaker-count settings are stored, then trace the automatic steps that depend on them. Done should mean users can change those properties and rerun the dependent steps, with suitable coverage for the workflow.

Written by the indexing model from the issue text.