chore: add sproutclaw git workflow and track local extensions

Document main/upstream-sync/feature branch strategy, add sync/push
scripts, track .pi/agent extensions and webui in git, and disable
startup changelog via showChangelogOnStartup.

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

.pi/agent/extensions/exit-command.ts

@@ -0,0 +1,17 @@
+/**
+ * Exit Command Extension
+ *
+ * 添加 /exit 命令用于退出 pi Agent
+ */
+
+import type { ExtensionAPI } from "@mariozechner/pi-coding-agent";
+
+export default function (pi: ExtensionAPI) {
+	pi.registerCommand("exit", {
+		description: "退出 pi Agent",
+		handler: async (_args, ctx) => {
+			ctx.ui.notify("正在退出...", "info");
+			ctx.shutdown();
+		},
+	});
+}