Better handle no-op updates

It's possible today to get a no-op update where e.g. just metadata like labels change. We should definitely detect this and highlight the no-op nature of the change; probably just default to "live updating" the origin? Should we record that transition at all though (just in the journal)?.

No files, tests, or entry points are named. Start by tracing the update and journal behavior described in issue #205, then resolve what qualifies as a no-op and whether it should update the origin or be recorded in the journal; done means those behaviors are explicitly decided and covered.

Vom Indexierungsmodell aus dem Issue-Text verfasst.