CLI --load interrupt e2e: SIGTERM case exits by signal (code null) under load #2973

Problem

clients/cli/__tests__/load-interrupt-e2e.test.ts › "prints the partial summary and exits 130 on one SIGTERM" fails intermittently under machine load: the child's exit code is null (it died by the signal) instead of 130.

AssertionError: expected null to be 130
 ❯ __tests__/load-interrupt-e2e.test.ts:141:20
    139|       run.child.kill(signal);
    140|       const { code, stdout, stderr } = await run.done;
    141|       expect(code).toBe(EXIT_CODES.INTERRUPTED);

Observed while working #2922 (which touches only clients/mcpdo tests): it failed the local:gate coverage stage once, and in isolated reruns of just this file it failed 3 of 6 times with the load average around 17–22 (several concurrent agent gates). Passes on a quiet run.

Expected

The case is deterministic: either the CLI's signal handler is guaranteed to be installed before the test sends the signal (and the test waits on that condition rather than calls >= 10), or the CLI's handling is fixed if a real window exists where a SIGTERM kills it outright mid---load. Per AGENTS.md, a race is fixed with an awaited condition, never headroom.