Summary

Fixes the pre-existing account-routing Behavior-test failure by correcting the test synchronization bound, not product code.

The unchanged product reaches endpoint creation and preserves the concurrent metadata extension in about seven seconds on this machine. The test previously failed after five seconds, so its deadline was stale under load.

Change

• Extend the endpoint marker wait from 5 seconds to a bounded 30 seconds.
• Stop waiting early if the spawn exits.
• Reap a failed background spawn and include its captured output in the assertion failure.
• Preserve the original metadata-lock assertion unchanged.

Verification

• FM_TEST_FOCUSED=review-round-16 tests/fm-account-routing.test.sh passed all three focused lifecycle cases.
• bash tests/fm-account-routing.test.sh passed ok - off-mode metadata merge-and-replace serializes with extension writers, then later hit only the separately tracked load-induced session sync race never reached managed account cleanup timing flake.
• bin/fm-lint.sh passed with pinned ShellCheck 0.11.0.
• git diff --check passed.

This branch does not modify tests/fm-secondmate-harness.test.sh.