*: improve automated workflows

[KaloyanTanev]

Some small QoL improvements over the workflows.

[Copilot]

Pull request overview

Improves the reliability and observability of the automated “rebase + tag” workflows by switching from output-grep heuristics to exit-code based success detection, adding a post-rebase verification step before tagging, and tightening what gets pushed.

Changes:

• Capture git rebase output once, use the exit code to set a success output, and abort failed rebases to leave a clean working tree for retries.
• Add a git range-diff verification gate to ensure *-obol tags are patch-identical to “upstream tag + obol changes” before tagging.
• Push only the newly created tag ref instead of all tags.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
.github/workflows/tag.yml	Adds exit-code based rebase handling, introduces range-diff verification gating for tagging, and pushes only the new tag ref.
.github/workflows/sync-rebase.yml	Switches rebase success detection to exit code, persists output cleanly, and gates push on a boolean success output.

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