ci: fix agentpaas install path (agentpaas/, not root)

repo 根目录无 pyproject.toml; agentpaas/pyproject.toml 才是 agentpaas 包定义。
上轮 CI 在 'pip install -e .' 时 ERROR: ... does not appear to be a Python project.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.github/workflows/ci.yml

@@ -44,7 +44,7 @@ jobs:
       - name: Install lambdagent (src-layout) + agentpaas
         run: |
           pip install -e lambdagent/
-          pip install -e .   # agentpaas + 它的 fastapi/uvicorn/pydantic 等依赖
+          pip install -e agentpaas/   # agentpaas + fastapi/uvicorn/pydantic 依赖
           pip install pytest pytest-asyncio
       - name: Run tests
         run: python -m pytest tests/ -v --tb=short
@@ -66,7 +66,7 @@ jobs:
       - name: Install both packages
         run: |
           pip install -e lambdagent/
-          pip install -e .   # agentpaas needs fastapi/uvicorn/pydantic
+          pip install -e agentpaas/   # agentpaas needs fastapi/uvicorn/pydantic
       - name: Verify package surface
         run: |
           python -c "import lambdagent; print(f'lambdagent OK: {len(lambdagent.__all__)} exports')"