fix: release-check lint fixes for 1.1.0 publish

Wrap long lines for flake8, rename extensions remove command handler
to avoid Click shadowing, and drop unused migration imports.

src/kaizen_agentic/extensions.py

@@ -438,7 +438,10 @@ version: {extension.version}
         agent_content += "---\n\n"
         agent_content += f"# {extension.name}\n\n"
         agent_content += f"{extension.description}\n\n"
-        agent_content += f"This agent extends **{extension.base_agent}** with project-specific functionality.\n\n"
+        agent_content += (
+            f"This agent extends **{extension.base_agent}** "
+            f"with project-specific functionality.\n\n"
+        )
 
         if extension.configuration.get("custom_instructions"):
             agent_content += "## Custom Instructions\n\n"