FR: Detect manifest changes and automatically run lock

Currently, the lock generation is manual, and sometimes forgotten after manifest changes, it would be nice to detect manifest changes. and trigger lock generation and update the lockfile in place.

Start by locating the manifest, lock-generation process, and lockfile handling in the repository. Determine how manifest changes can trigger lock generation and how the lockfile should be updated in place; done means those changes no longer require a manual lock-generation step.

Written by the indexing model from the issue text.