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/backend/http/server.ts

@@ -0,0 +1,36 @@
+import { createServer, type IncomingMessage, type ServerResponse } from "node:http";
+import { applyCorsHeaders } from "./cors.ts";
+import { serveStatic } from "./static.ts";
+import { handleChatRoute } from "../routes/chat.ts";
+import { handleCommandsRoute } from "../routes/commands.ts";
+import { handleModelsRoute } from "../routes/models.ts";
+import { handleSessionsRoute } from "../routes/sessions.ts";
+import { handleSettingsRoute } from "../routes/settings.ts";
+import { handleWebuiConfigRoute } from "../routes/webui-config.ts";
+import type { WebUiContext } from "../types/context.ts";
+
+export function createWebUiServer(ctx: WebUiContext) {
+	return createServer((req: IncomingMessage, res: ServerResponse) => {
+		const url = new URL(req.url!, `http://localhost:${ctx.config.port}`);
+		const pathname = url.pathname;
+
+		if (pathname.startsWith("/api/") && applyCorsHeaders(req, res)) {
+			return;
+		}
+
+		if (req.method === "GET" && !pathname.startsWith("/api/")) {
+			serveStatic(ctx.config.paths.publicDir, pathname, req, res, true);
+			return;
+		}
+
+		if (handleChatRoute(req, res, ctx, pathname)) return;
+		if (handleSessionsRoute(req, res, ctx, pathname)) return;
+		if (handleModelsRoute(req, res, ctx, pathname)) return;
+		if (handleWebuiConfigRoute(req, res, ctx, pathname, url)) return;
+		if (handleSettingsRoute(req, res, ctx, pathname)) return;
+		if (handleCommandsRoute(req, res, ctx, pathname)) return;
+
+		res.writeHead(404);
+		res.end("Not found");
+	});
+}