Git tag references GA workflow which might be outdated

Reported by @mike0sv

Consider a case: you register a model version, promote it, and find out that Github Actions workflow is incorrect (commit 1). You fix it, commit and push, but now to trigger it again with the new workflow, you need to create a Git tag that references new commit (commit 2). To do that, you have to register new model version in commit 2, and promote it.

Often you fix CI workflow by trial-and-error, so it may happen you need to register many extra versions for the model.

GTO does an assumption that a single model version belongs to only one commit, thus you can't mark two commits as having the same model version (probably for good - the model could change). A workaround that comes to mind is to allow creation of Git tag that does a promotion of a version from commit 1, but references different commit - e.g. commit 2. It may look like this `model@v0.0.1#dev` (it's assumed that `v0.0.1` is registered in commit 1).

Start by tracing the CLI paths for model registration, promotion, and Git tag creation, focusing on how a GitHub Actions workflow uses the resulting tag. Define how a tag can promote a version registered at commit 1 while referencing commit 2, then verify that repeated workflow fixes do not require registering extra model versions.

Written by the indexing model from the issue text.