fix: inline skills prompt in dispatch_command auto-detection path

build_command_invocation() reads self._skills_mode which stays False
when skills mode is only auto-detected from the project layout. Inline
the /speckit-<stem> prompt construction so dispatch_command() sends the
correct prompt regardless of how skills mode was detected.

Also strengthen test_dispatch_detects_speckit_skills_layout to assert
the -p prompt contains /speckit-plan and the user args.

Author: mnriem

src/specify_cli/integrations/copilot/__init__.py

@@ -189,7 +189,9 @@ def dispatch_command(
                 )
 
         if skills_mode:
-            prompt = self.build_command_invocation(command_name, args)
+            prompt = f"/speckit-{stem}"
+            if args:
+                prompt = f"{prompt} {args}"
         else:
             agent_name = f"speckit.{stem}"
             prompt = args or ""

tests/integrations/test_integration_copilot.py

@@ -659,6 +659,13 @@ def test_dispatch_detects_speckit_skills_layout(self, tmp_path):
             assert "--agent" not in call_args, (
                 f"Skills mode should not use --agent, got: {call_args}"
             )
+            prompt = call_args[call_args.index("-p") + 1]
+            assert "/speckit-plan" in prompt, (
+                f"Skills mode prompt should invoke /speckit-plan, got: {prompt}"
+            )
+            assert "my args" in prompt, (
+                f"Skills mode prompt should preserve user args, got: {prompt}"
+            )
 
     # -- Next-steps display for Copilot skills mode -----------------------