feat(cli): S4 follow-up, refusal backoff and tracker boot (row 45, #1527)

Rocko's round 2 candidate, packet agents/rocko/work/s4-follow-up/
(build.patch c8cec070, candidate manifest 5b067a9d, 8/8 OK).

- Definite DM refusals wait the full 30-minute cap, counted from the
  journal's last refusal, so five refusals span about two hours before
  gave-up (lead decision 73). Unknown outcomes keep doubling.
- Broker close sends at host.mjs:144/150/184/188 pass a callback, which
  closes the EPIPE window both reviewers found in round 1.
- README documents manual recovery for an open decision.
- trackers-boot test, X9, X14, and Darkwing's round 1 notes 1-4.
- The append type check stays out; Rocko's reason holds (both reviewers
  agree).

Reviews: Darkwing approve (comment 26884), Filbert approve (26886).
Landing gate on b13fef4c plus the patch: every node suite and every
scripts/test-*.sh green, test-task 98/0.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

packages/cli/src/host.mjs

@@ -141,13 +141,13 @@ export async function startHost({ boot, business, notifier = null, bootTimeoutMs
     } catch (e) {
       notify.kill("SIGTERM");
       await ended(notify, 5000);
-      broker.send({ op: "close" });
+      if (broker.connected) broker.send({ op: "close" }, () => {});
       await ended(broker, CLOSE_TIMEOUT_MS);
       throw e;
     }
     if (ok?.ok !== true) {
       await ended(notify, 5000);
-      broker.send({ op: "close" });
+      if (broker.connected) broker.send({ op: "close" }, () => {});
       await ended(broker, CLOSE_TIMEOUT_MS);
       throw new CliError(`notifier refused to start: ${typeof ok?.error === "string" ? ok.error : "notifier-refused"}`, 3);
     }
@@ -181,11 +181,11 @@ export async function startHost({ boot, business, notifier = null, bootTimeoutMs
     closing = true;
     let result = code;
     if (notify) {
-      if (notify.connected) notify.send({ op: "stop" });
+      if (notify.connected) notify.send({ op: "stop" }, () => {});
       if ((await ended(notify, CLOSE_TIMEOUT_MS)) !== 0 && result === 0) result = 1;
     }
     await queue;
-    if (broker.connected) broker.send({ op: "close" });
+    if (broker.connected) broker.send({ op: "close" }, () => {});
     if ((await ended(broker, CLOSE_TIMEOUT_MS)) !== 0 && result === 0) result = 1;
     const now = readHostState(dataRoot);
     if (now && now.pid === state.pid && now.startTime === state.startTime) rmSync(hostFile(dataRoot), { force: true });