docs: complete Epic FEATURES-20260305-085909-JDI Integrate Superpowers Workflows

[julwrites]

The Epic FEATURES-20260305-085909-JDI Integrate Superpowers Workflows is completed.
All sub-tasks for phases 1 through 3 have been implemented and checked off in the Epic description.
The "Local Review" step in AGENTS.md and docs/tasks/GUIDE.md is no longer marked as "(coming soon)" since scripts/review.py is fully implemented. The templates/GUIDE.md has been aligned to reflect the newly introduced Superpower Workflows as well.

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PR created automatically by Jules for task 1236791802814710726 started by @julwrites

[google-labs-jules]

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