fix systemd: use startup.sh instead of inline ExecStartPre

Multi-line Python in ExecStartPre is invalid systemd syntax.
Extract pip install + reranker self-test into startup.sh.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

rag-worker/startup.sh

@@ -0,0 +1,21 @@
+#!/bin/bash
+# zhixi-worker startup checks — called by systemd ExecStartPre
+set -e
+cd /opt/zhixi/backend/rag-worker
+
+# Install any new dependencies
+/usr/bin/python3.11 -m pip install -q -r requirements.txt \
+  -i https://mirrors.tencentyun.com/pypi/simple
+
+# Self-test: reranker
+/usr/bin/python3.11 -c "
+import asyncio
+from reranker import rerank
+async def t():
+    r = await rerank('测试', ['这是测试文本', '无关内容'], top_n=1)
+    if not r:
+        raise RuntimeError('reranker returned empty')
+    print(f'[self-test] reranker OK, score={r[0][\"score\"]:.4f}')
+asyncio.run(t())
+print('[self-test] all checks passed')
+"

rag-worker/zhixi-worker.service

@@ -9,19 +9,7 @@ WorkingDirectory=/opt/zhixi/backend/rag-worker
 Environment="PYTHONUNBUFFERED=1"
 EnvironmentFile=/opt/zhixi/backend/rag-worker/.env
 
-# Install deps and self-test before starting main loop
-ExecStartPre=/usr/bin/python3.11 -m pip install -q -r /opt/zhixi/backend/rag-worker/requirements.txt -i https://mirrors.tencentyun.com/pypi/simple
-ExecStartPre=/usr/bin/python3.11 -c "
-import asyncio, sys
-from reranker import rerank
-async def t():
-    r = await rerank('测试', ['这是测试文本', '无关内容'], top_n=1)
-    if not r: raise RuntimeError('reranker returned empty')
-    print(f'[self-test] reranker OK, score={r[0][\"score\"]:.4f}')
-asyncio.run(t())
-print('[self-test] all checks passed')
-"
-
+ExecStartPre=/bin/bash /opt/zhixi/backend/rag-worker/startup.sh
 ExecStart=/usr/bin/python3.11 -u main.py
 Restart=always
 RestartSec=5