feat(pi): finish subagent runtime surfaces

modules/agents/pi/extensions/subagents/ui.ts

@@ -0,0 +1,28 @@
+import type { SubagentStatus } from "./types.ts";
+
+export function renderSummary(statuses: SubagentStatus[]): string[] {
+  const running = statuses.filter((status) => ["starting", "running", "settling"].includes(status.state)).length;
+  const queued = statuses.filter((status) => status.state === "queued").length;
+  const terminal = statuses.filter((status) => ["completed", "failed", "cancelled", "timed_out", "orphaned"].includes(status.state)).length;
+  if (running === 0 && queued === 0 && terminal === 0) return [];
+  return [`subagents: ${running} running · ${queued} queued · ${terminal} recent`];
+}
+
+export function renderInspector(statuses: SubagentStatus[]): string[] {
+  const lines = renderSummary(statuses);
+  for (const status of statuses) {
+    lines.push(
+      `${status.id} ${status.label} ${status.context} ${status.state} ${Math.round(status.elapsedMs / 1000)}s ${status.model ?? "inherit"} ${status.tools} ${status.lastEvent ?? "none"} result:${status.resultAvailable ? "yes" : "no"}`,
+    );
+  }
+  return lines;
+}
+
+export function widget(statuses: SubagentStatus[], expanded: boolean) {
+  return () => ({
+    invalidate() {},
+    render(width: number) {
+      return (expanded ? renderInspector(statuses) : renderSummary(statuses)).map((line) => (line.length > width ? line.slice(0, Math.max(0, width - 1)) : line));
+    },
+  });
+}