Add Community Friends section to README (#1956)

* Add Community Friends section with cc-sdd

Adds a new "Community Friends" section to the README for projects that
extend or build on Spec Kit. Starts with cc-sdd, a Claude Code plugin
that layers composable traits (quality gates, worktree isolation, agent
teams) on top of Spec Kit's core workflow.

Suggested by @mnriem in discussion #1889.

Assisted-By: 🤖 Claude Code

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* Update cc-sdd repo URL after rename

Assisted-By: 🤖 Claude Code

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* Mention Superpowers explicitly in cc-sdd description

Assisted-By: 🤖 Claude Code

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

README.md

@@ -35,6 +35,7 @@
 - [📋 Detailed Process](#-detailed-process)
 - [🔍 Troubleshooting](#-troubleshooting)
 - [💬 Support](#-support)
+- [🤝 Community Friends](#-community-friends)
 - [🙏 Acknowledgements](#-acknowledgements)
 - [📄 License](#-license)
 
@@ -783,6 +784,14 @@ rm gcm-linux_amd64.2.6.1.deb
 
 For support, please open a [GitHub issue](https://github.com/github/spec-kit/issues/new). We welcome bug reports, feature requests, and questions about using Spec-Driven Development.
 
+## 🤝 Community Friends
+
+Projects that extend, visualize, or build on Spec Kit:
+
+| Project | Description |
+|---------|-------------|
+| [cc-sdd](https://github.com/rhuss/cc-sdd) | Claude Code plugin that adds composable traits on top of Spec Kit: [Superpowers](https://github.com/obra/superpowers)-based quality gates, spec/code review, git worktree isolation, and parallel implementation via agent teams. |
+
 ## 🙏 Acknowledgements
 
 This project is heavily influenced by and based on the work and research of [John Lam](https://github.com/jflam).