backend/frontend/runtime: 训练面板 / session 隔离 / agent runtime 调整

- backend/api/server.py：训练 step-detail / pipeline 卡片排序逻辑
- frontend：thread-list / thread / training-pipeline-panel / step-detail-sheet 配套调整，新增 metrics-chart-panel
- src/agent_*：tool spec / runtime / prompting 配套
- .gitignore 加 .logs/

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

.gitignore

@@ -21,6 +21,7 @@ archive/
 scratchpad/
 tasks/
 router_session_parquet/
+.logs/
 
 # Environment files
 .env