test(herdr): fix Quick Start close test on Linux CI (util-linux script syntax)

[lis186]

摘要

main 從 #544 起 CI 一直紅在 Herdr Quick Start close › exits the process when the menu is closed：測試用 BSD 語法呼叫 script，util-linux（ubuntu CI）不接受位置參數命令，onboarding 從未啟動、marker 永遠不出現，兩個 Node job 確定性失敗。本 PR 依平台分支 script 呼叫方式，並順手修掉測試在 macOS 上每次吃滿 30s timeout 的假延遲（→ ~250ms）。

Root cause

• BSD script (macOS): script -q /dev/null <command...> — command as positional args.
• util-linux script (ubuntu CI): only accepts a command via -c; positional operands after the file are rejected, so the wrapper exited immediately. The inner command (and its >/dev/null 2>&1) swallowed the error, the marker was never written, and the poll printed LINGERED — deterministic on both Node 20 and 22, every push since the test landed on main.

Changes

• Branch on process.platform: Linux uses script -qec "<cmd>" /dev/null, macOS keeps the BSD positional form.
• Redirect the background job as a whole: the keystroke-feeder subshell's inherited stderr was holding spawnSync's pipe open until its sleep ended, so even a passing run ate the full 30s timeout. Sleep shrinks 40s → 12s (still well past the 8s poll window).

Verification

• fail-on-old: every main CI run since bd726f2 fails on exactly this test with actual: LINGERED (runs 31993589901, 32014062729, plus the PR Mark a Herdr badge whose numbers the transcript has outrun, and rescan to fix it #553 run 32010319418).
• pass-on-new (macOS branch): full test/herdr-plugin.test.js 132/132 green locally with isolated CCXRAY_HOME; the fixed test now completes in ~250ms instead of 30s.
• pass-on-new (Linux branch): no util-linux script available locally — this PR's own CI run is the differential evidence.

Note: run 31994476657 (#545) also had a one-off count_tokens e2e failure ("proxy did not start") that does not reproduce in the other runs — flaky, not addressed here.

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