.harness 并行污染 flake：design-signoff 测试的 fixture phase 建在真实 phases/，被 lint-third-artifact 扫描撞 ENOENT

全量 .harness suite 并行时偶发：`lint-third-artifact.test.ts` 的「真实仓库状态必须绿」用例 scandir 到 `phases/phase-zz-signoff-test-fixture/contracts` 时目录正被 design-signoff.test.ts 删除 → ENOENT 红。sync-github.test.ts 同款 fixture 模式（phase-zz-sync-test-fixture）。

候选修法：① fixture 迁 tmpdir + 函数收 phasesRoot 参数；② 扫描器排除 `*-fixture` 后缀 + 容忍 scandir ENOENT（目录本可随时消失）；③ 真实状态用例快照 phases 列表时过滤 fixture。归 harness 线。2026-08-12 05:1x coord-main 在 #1010 修复过程中撞见，证据在该夜循环记录。

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Start by reading .harness/lint-third-artifact.test.ts, design-signoff.test.ts, and sync-github.test.ts, then review the evidence from issue #1010. Run the full .harness suite in parallel to reproduce the ENOENT. Done means the real-repository-state test remains green without fixture races or missing-directory failures.

Written by the indexing model from the issue text.