docs(skills): clarify overwrite_existing behavior

Author: RbBtSn0w

src/specify_cli/__init__.py

@@ -1533,8 +1533,9 @@ def install_ai_skills(
         project_path: Target project directory.
         selected_ai: AI assistant key from ``AGENT_CONFIG``.
         tracker: Optional progress tracker.
-        overwrite_existing: When True, overwrite existing ``SKILL.md`` files
-            generated by previous runs. Defaults to False.
+        overwrite_existing: When True, overwrite any existing ``SKILL.md`` file
+            in the target skills directory (including user-authored content).
+            Defaults to False.
 
     Returns:
         ``True`` if at least one skill was installed or all skills were