fix: correct Copilot extension command registration (#1724)

* fix: correct Copilot extension command registration (#copilot)

- Use .agent.md extension for commands in .github/agents/
- Generate companion .prompt.md files in .github/prompts/
- Clean up .prompt.md files on extension removal
- Add tests for Copilot-specific registration behavior

Bumps version to 0.1.7.

* fix: test copilot prompt cleanup via ExtensionManager.remove() instead of manual unlink

---------

Co-authored-by: Ismael <ismael.jimenez-martinez@bmw.de>

CHANGELOG.md

@@ -7,6 +7,15 @@ Recent changes to the Specify CLI and templates are documented here.
 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).
 
+## [0.1.13] - 2026-03-03
+
+### Fixed
+
+- **Copilot Extension Commands Not Visible**: Fixed extension commands not appearing in GitHub Copilot when installed via `specify extension add --dev`
+  - Changed Copilot file extension from `.md` to `.agent.md` in `CommandRegistrar.AGENT_CONFIGS` so Copilot recognizes agent files
+  - Added generation of companion `.prompt.md` files in `.github/prompts/` during extension command registration, matching the release packaging behavior
+  - Added cleanup of `.prompt.md` companion files when removing extensions via `specify extension remove`
+
 ## [0.1.12] - 2026-03-02
 
 ### Changed