enable collectoss to detect its own collection state (full collection/idle/collection running/stopped)

> [!NOTE]
> Migrated from [augurlabs/augur#3775](https://github.com/augurlabs/augur/issues/3775)
> Originally opened by `@MoralCode` on 2026-03-17

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It may be useful for testing purposes to add an option (via a special command line flag or config option or something) to have augur stop and shut itself down once it hits full collection and all tasks go idle.

this would be intended for instances with VERY few small repos (1-5) that are being run in a CI-like environment, such as for automated end-to-end testing (as is the usecase for the parent issue)