swarm: list subagents from their published run state

The subagents list reads each subagent's status from the subagent-status
bucket and reports its state, when it began and the exit status. A subagent
with no status keeps the newest-row lookup, so an older daemon lists as before.
The swarm UI uses the state when there is one and the row-age guess otherwise.

frontend/packages/swarm-ui/test/subagent-list.test.mjs

@@ -6,10 +6,12 @@ import { test } from "node:test";
 import {
   STALE_S,
   byRecency,
+  isDimmed,
   isRunning,
   runLabel,
   runningLabel,
   splitRunning,
+  stateLabel,
   stillListed,
 } from "../src/agent/terminal/subagent-list.ts";
 
@@ -73,6 +75,58 @@ test("a pick holds only while the refreshed list still has it", () => {
   assert.equal(stillListed(null, subs), null);
 });
 
+const withState = (name, state, sinceAgo, rowAgo = null) => ({
+  ...sub(name, rowAgo),
+  state,
+  since_unix: NOW - sinceAgo,
+  exit: state === "finished" ? 0 : null,
+});
+
+test("a published state decides, whatever the newest row's age says", () => {
+  // Quiet for an hour but the daemon says running: thinking, not stopped.
+  assert.equal(isRunning(withState("a", "running", 3600, 3600), NOW), true);
+  // A row a second ago but the daemon says finished.
+  assert.equal(isRunning(withState("a", "finished", 5, 1), NOW), false);
+  assert.equal(isRunning(withState("a", "stale", 900), NOW), false);
+});
+
+test("only a subagent without a status falls back to the row's age", () => {
+  assert.equal(isDimmed(sub("a", STALE_S + 1), NOW), true);
+  assert.equal(isDimmed(sub("a", 5), NOW), false);
+  assert.equal(isDimmed(sub("a", null), NOW), false);
+  assert.equal(isDimmed(withState("a", "running", 3600, 3600), NOW), false);
+  assert.equal(isDimmed(withState("a", "finished", 5, 1), NOW), true);
+  assert.equal(isDimmed(withState("a", "stale", 5), NOW), true);
+});
+
+test("the state word names finished and stale subagents only", () => {
+  assert.equal(stateLabel(withState("a", "finished", 5)), "finished");
+  assert.equal(stateLabel(withState("a", "stale", 5)), "stopped reporting");
+  assert.equal(stateLabel(withState("a", "running", 5)), "");
+  assert.equal(stateLabel(sub("a", 5)), "");
+});
+
+test("a subagent with only a status sorts by when its state began", () => {
+  const list = [
+    withState("old", "finished", 500),
+    sub("row", 100),
+    withState("new", "running", 5),
+  ];
+  assert.deepEqual(
+    [...list].sort(byRecency).map((s) => s.name),
+    ["new", "row", "old"],
+  );
+  const { running, quiet } = splitRunning(list, NOW);
+  assert.deepEqual(
+    running.map((s) => s.name),
+    ["new", "row"],
+  );
+  assert.deepEqual(
+    quiet.map((s) => s.name),
+    ["old"],
+  );
+});
+
 test("the run label names the model and effort, whichever are known", () => {
   assert.equal(runLabel({ model: "opus", effort: "high" }), "opus · high");
   assert.equal(runLabel({ model: "opus", effort: null }), "opus");