git-refs pre-push: show push progress instead of a silent stall

The git-refs pre-push path pushed the queued checkpoint refs via batchPushRefs with no output, so pushing a large backlog (e.g. a freshly migrated repo) looked like git had hung for 30+ seconds while git push reported only "Everything up to date" for the branch.

Mirror the v1-branch path's progress line: print "[entire] Pushing N checkpoint ref(s) to <target>..." with the shared startProgressDots ticker to stderr (which git surfaces during the pre-push hook), and a " done" / "pushed X of N" suffix. The per-ref fetch+replay recovery path gets its own progress line too.