feat: add superpowers bridge extension to community catalog (#2023)

* docs: correct specify extension add syntax to require extension name

The specify extension add command requires the extension name as a positional argument. Many documentation files incorrectly demonstrated using the --from flag without specifying the extension name first.

* feat: add superb extension to community catalog

Orchestrates obra/superpowers skills within the spec-kit SDD workflow.

* fix: link superb extension docs