dotfiles: add interactive pi planner workflow

.pi/agent/extensions/subagent/jsonl.ts

@@ -0,0 +1,40 @@
+import { StringDecoder } from "node:string_decoder";
+
+export function serializeJsonLine(value: unknown): string {
+	return `${JSON.stringify(value)}\n`;
+}
+
+export function attachJsonlLineReader(stream: NodeJS.ReadableStream, onLine: (line: string) => void): () => void {
+	const decoder = new StringDecoder("utf8");
+	let buffer = "";
+
+	const emitLine = (line: string) => {
+		onLine(line.endsWith("\r") ? line.slice(0, -1) : line);
+	};
+
+	const onData = (chunk: Buffer | string) => {
+		buffer += typeof chunk === "string" ? chunk : decoder.write(chunk);
+		while (true) {
+			const newlineIndex = buffer.indexOf("\n");
+			if (newlineIndex === -1) return;
+			emitLine(buffer.slice(0, newlineIndex));
+			buffer = buffer.slice(newlineIndex + 1);
+		}
+	};
+
+	const onEnd = () => {
+		buffer += decoder.end();
+		if (buffer.length > 0) {
+			emitLine(buffer);
+			buffer = "";
+		}
+	};
+
+	stream.on("data", onData);
+	stream.on("end", onEnd);
+
+	return () => {
+		stream.off("data", onData);
+		stream.off("end", onEnd);
+	};
+}