fix(ci): clear leftover .venv before Python 3.14 venv create (BUG-677)

Staging gate run 2594 died in Install dependencies with FileExistsError on a reused hostexecutor .venv. Remove the leftover directory and create the venv with --clear so Python 3.14 mkdir does not abort the job.

.gitea/workflows/backend-quality-gate.yml

@@ -235,7 +235,10 @@ jobs:
           NPM_CONFIG_REGISTRY: https://registry.npmmirror.com
         run: |
           set -euo pipefail
-          python3 -m venv .venv
+          # Hostexecutor may keep a gitignored .venv/; Python 3.14 mkdir then
+          # raises FileExistsError. Clear first instead of reusing leftovers.
+          rm -rf -- .venv
+          python3 -m venv --clear .venv
           export PATH="$PWD/.venv/bin:$PATH"
           python -m pip install --upgrade pip
           python -m pip install \

docs/BUG_HISTORY.md

@@ -10532,3 +10532,19 @@
 - 相关记录：BUG-442
 - 复发自：无
 - 修复版本：待发布
+
+## BUG-677 | staging quality gate 在残留 .venv 上被 Python 3.14 mkdir 打断
+
+- 状态：resolved
+- 首次发现：2026-09-14
+- 最近更新：2026-09-14
+- 影响面：Gitea `Independent Staging Quality Gate` validate「Install dependencies」、publish（因 `needs: validate` 被 skip）
+- 用户现象：推送 `69ffa07d` 后门禁 run `2594` 约 20 秒失败；测试、lint、build 未执行，publish/deploy skipped。
+- 触发条件：`runs-on: xiaoxin` 的 act_runner hostexecutor 复用 job 目录且已有 gitignored `.venv/`；runner 报告 `Python 3.14.4`。
+- 根因：`python3 -m venv .venv` 对已存在目录执行 `mkdir`，Python 3.14 抛出 `FileExistsError: [Errno 17] File exists: '.../hostexecutor/.venv'`。`git status --porcelain --untracked-files=all` 仍为空，因为忽略目录不出现在 porcelain 里。不是 pip、npm 或校正测试失败。
+- 修复：安装步骤先 `rm -rf -- .venv`，再 `python3 -m venv --clear .venv`。不改测试、lint、build、exact-SHA 与镜像发布语义。
+- 验证：`frontend/tests/staging-backend-workflows.test.ts` 锁定清除后再 `--clear`；Gitea gate 对修复 SHA 复跑。
+- 防复发：质量门创建 `.venv` 必须允许 hostexecutor 残留目录。不得把 Python 3.14 `FileExistsError` 当成业务测试失败。
+- 相关记录：BUG-149、BUG-364
+- 复发自：无
+- 修复版本：待发布

frontend/tests/staging-backend-workflows.test.ts

@@ -227,7 +227,11 @@ test("Gitea quality gate validates before publishing an immutable ACR manifest",
   assert.equal((workflow.match(/exact staging gate checkout failed after \$attempt bounded attempts/g) ?? []).length, 2);
   assert.equal((workflow.match(/\[\[ "\$fetch_succeeded" == true \]\]/g) ?? []).length, 2);
   assert.doesNotMatch(workflow, /http\.lowSpeedLimit=1024|http\.lowSpeedTime=30/);
-  assert.match(workflow, /python3 -m venv \.venv/);
+  // 原值: python3 -m venv .venv
+  // 新值: rm -rf leftover then python3 -m venv --clear .venv
+  // 原因: BUG-677 Python 3.14 FileExistsError on reused hostexecutor .venv
+  assert.match(workflow, /rm -rf -- \.venv\n\s+python3 -m venv --clear \.venv/);
+  assert.doesNotMatch(workflow, /python3 -m venv \.venv(?:\s|$)/);
   assert.match(workflow, /PIP_INDEX_URL: https:\/\/mirrors\.aliyun\.com\/pypi\/simple\//);
   assert.match(workflow, /NPM_CONFIG_REGISTRY: https:\/\/registry\.npmmirror\.com/);
   for (const constraint of [
@@ -272,6 +276,8 @@ test("Gitea quality gate validates before publishing an immutable ACR manifest",
   const installStep = workflow.match(
     /- name: Install dependencies[\s\S]*?(?=\n\s+- name: Validate backend, package, frontend, and database contracts)/,
   )?.[0] ?? "";
+  assert.match(installStep, /rm -rf -- \.venv/);
+  assert.match(installStep, /python3 -m venv --clear \.venv/);
   assert.match(installStep, /workdir="\$\(pwd -P\)"/);
   assert.match(installStep, /docker run --rm/);
   assert.doesNotMatch(installStep, /timeout --signal=TERM --kill-after=30s 900s docker run/);