chore: import upstream snapshot with attribution

extensions/template/CHANGELOG.md

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+# Changelog
+
+All notable changes to this extension will be documented in this file.
+
+The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
+and this project adheres to  [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
+
+## [Unreleased]
+
+### Planned
+
+- Feature ideas for future versions
+- Enhancements
+- Bug fixes
+
+## [1.0.0] - YYYY-MM-DD
+
+### Added
+
+- Initial release of extension
+- Command: `/speckit.my-extension.example` - Example command functionality
+- Configuration system with template
+- Documentation and examples
+
+### Features
+
+- Feature 1 description
+- Feature 2 description
+- Feature 3 description
+
+### Requirements
+
+- Spec Kit: >=0.1.0
+- External dependencies (if any)
+
+---
+
+[Unreleased]: https://github.com/your-org/spec-kit-my-extension/compare/v1.0.0...HEAD
+[1.0.0]: https://github.com/your-org/spec-kit-my-extension/releases/tag/v1.0.0