feat(sproutclaw): modularize webui, extensions, and agent config layout

Restructure local extensions into per-feature directories, split WebUI
into backend modules with slash commands and systemd support, and track
prompts/skills under .pi/agent for portable Gitea deployment.

Co-authored-by: Cursor <cursoragent@cursor.com>

.pi/agent/extensions/webui/frontend/src/main.tsx

@@ -1,5 +1,6 @@
 import { StrictMode } from "react";
 import { createRoot } from "react-dom/client";
+import "@mogeko/maple-mono-cn/dist/font/result.css";
 import { App } from "./App";
 import "./styles/global.css";