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>

src/specify_cli/extensions.py

@@ -455,6 +455,12 @@ class ExtensionManager:
                     if cmd_file.exists():
                         cmd_file.unlink()
 
+                    # Also remove companion .prompt.md for Copilot
+                    if agent_name == "copilot":
+                        prompt_file = self.project_root / ".github" / "prompts" / f"{cmd_name}.prompt.md"
+                        if prompt_file.exists():
+                            prompt_file.unlink()
+
         if keep_config:
             # Preserve config files, only remove non-config files
             if extension_dir.exists():
@@ -597,7 +603,7 @@ class CommandRegistrar:
             "dir": ".github/agents",
             "format": "markdown",
             "args": "$ARGUMENTS",
-            "extension": ".md"
+            "extension": ".agent.md"
         },
         "cursor": {
             "dir": ".cursor/commands",
@@ -871,16 +877,40 @@ class CommandRegistrar:
             dest_file = commands_dir / f"{cmd_name}{agent_config['extension']}"
             dest_file.write_text(output)
 
+            # Generate companion .prompt.md for Copilot agents
+            if agent_name == "copilot":
+                self._write_copilot_prompt(project_root, cmd_name)
+
             registered.append(cmd_name)
 
             # Register aliases
             for alias in cmd_info.get("aliases", []):
                 alias_file = commands_dir / f"{alias}{agent_config['extension']}"
                 alias_file.write_text(output)
+                # Generate companion .prompt.md for alias too
+                if agent_name == "copilot":
+                    self._write_copilot_prompt(project_root, alias)
                 registered.append(alias)
 
         return registered
 
+    @staticmethod
+    def _write_copilot_prompt(project_root: Path, cmd_name: str) -> None:
+        """Generate a companion .prompt.md file for a Copilot agent command.
+
+        Copilot requires a .prompt.md file in .github/prompts/ that references
+        the corresponding .agent.md file in .github/agents/ via an ``agent:``
+        frontmatter field.
+
+        Args:
+            project_root: Path to project root
+            cmd_name: Command name (used as the file stem, e.g. 'speckit.my-ext.example')
+        """
+        prompts_dir = project_root / ".github" / "prompts"
+        prompts_dir.mkdir(parents=True, exist_ok=True)
+        prompt_file = prompts_dir / f"{cmd_name}.prompt.md"
+        prompt_file.write_text(f"---\nagent: {cmd_name}\n---\n")
+
     def register_commands_for_all_agents(
         self,
         manifest: ExtensionManifest,