feat: reduce default max_agent_step to 3 and refactor shell execution

- Lower default max_agent_step from 30 to 3 across all agent runners
  (coze, dashscope, deerflow, dify) for faster responses
- Refactor ExecuteShellTool to use plumbum with session-based isolation,
  maintaining shell state per session (cwd, env vars, etc.)
- Remove unused API-specific environment variables from cmd_run
- Fix data access bug in shipyard_neo._maybe_model_dump
- Add plumbum>=1.10.0 dependency

.gitignore

@@ -65,3 +65,4 @@ GenieData/
 .worktrees/
 
 .env
+dashboard/warker.js