feat(orchestration): add orchestration system with task scheduling

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

backend/app/agents/orchestration/task_graph.py

@@ -0,0 +1,128 @@
+from __future__ import annotations
+
+from uuid import uuid4
+
+from app.agents.schemas.orchestration import ParallelWorthiness, TaskGraph, TaskNode
+
+
+ROLE_KEYWORDS: list[tuple[str, tuple[str, ...]]] = [
+    ("librarian", ("查", "检索", "资料", "文档", "知识库", "年报", "forum", "search")),
+    ("analyst", ("分析", "判断", "风险", "总结", "对比", "洞察", "结论")),
+    ("schedule_planner", ("计划", "安排", "下周", "日程", "提醒", "优先级")),
+    ("executor", ("执行", "创建", "更新", "落库", "提交", "发帖")),
+]
+
+
+def build_bounded_task_graph(
+    *,
+    query_text: str,
+    parallel_worthiness: ParallelWorthiness,
+    max_nodes: int = 4,
+) -> TaskGraph | None:
+    roles = _infer_roles(query_text)
+    if not roles:
+        return None
+
+    independent_roles = roles[: min(max_nodes - 1, max(1, parallel_worthiness.estimated_subtasks))]
+    nodes: list[TaskNode] = []
+
+    for index, role in enumerate(independent_roles, start=1):
+        node_id = f"task-{index}-{uuid4().hex[:6]}"
+        nodes.append(
+            TaskNode(
+                node_id=node_id,
+                title=_build_title(role),
+                role=role,
+                goal=_build_goal(role, query_text),
+                depends_on=[],
+                execution_mode=(
+                    "parallel"
+                    if parallel_worthiness.preferred_mode in {"collaboration", "parallel"}
+                    and len(independent_roles) > 1
+                    else "serial"
+                ),
+                expected_evidence=_build_expected_evidence(role),
+            )
+        )
+
+    if len(nodes) > 1:
+        merge_id = f"merge-{uuid4().hex[:6]}"
+        nodes.append(
+            TaskNode(
+                node_id=merge_id,
+                title="汇总并收敛最终结论",
+                role="master",
+                goal="汇总前置子任务结果，形成统一可验证的输出。",
+                depends_on=[node.node_id for node in nodes],
+                execution_mode="serial",
+                expected_evidence=[{"type": "merge", "detail": "merged summary and conflict notes"}],
+            )
+        )
+
+    return TaskGraph(
+        nodes=nodes,
+        entry_node_ids=[node.node_id for node in nodes if not node.depends_on],
+        max_parallelism=max(1, len(independent_roles)),
+        rationale=_build_rationale(parallel_worthiness, independent_roles),
+    )
+
+
+def render_task_graph_summary(task_graph: TaskGraph | None) -> str | None:
+    if task_graph is None or not task_graph.nodes:
+        return None
+
+    lines = ["- 任务图:"]
+    for node in task_graph.nodes[:4]:
+        deps = f" deps={','.join(node.depends_on)}" if node.depends_on else ""
+        lines.append(f"  - [{node.execution_mode}] {node.title} ({node.role}){deps}")
+    return "\n".join(lines)
+
+
+def _infer_roles(query_text: str) -> list[str]:
+    selected: list[str] = []
+    text = query_text or ""
+    for role, keywords in ROLE_KEYWORDS:
+        if any(keyword in text for keyword in keywords):
+            selected.append(role)
+
+    if not selected:
+        return ["analyst"]
+    return selected
+
+
+def _build_title(role: str) -> str:
+    mapping = {
+        "librarian": "收集事实与外部/内部证据",
+        "analyst": "形成判断与风险分析",
+        "schedule_planner": "整理计划和优先级",
+        "executor": "执行必要操作并回收结果",
+    }
+    return mapping.get(role, "处理子任务")
+
+
+def _build_goal(role: str, query_text: str) -> str:
+    mapping = {
+        "librarian": f"围绕请求收集支持结论的事实和资料：{query_text}",
+        "analyst": f"基于当前请求输出结构化判断：{query_text}",
+        "schedule_planner": f"把当前请求收束为计划、安排或优先级：{query_text}",
+        "executor": f"基于请求执行必要动作并返回结果：{query_text}",
+    }
+    return mapping.get(role, query_text)
+
+
+def _build_expected_evidence(role: str) -> list[dict[str, str]]:
+    mapping = {
+        "librarian": [{"type": "evidence", "detail": "retrieval findings"}],
+        "analyst": [{"type": "analysis", "detail": "structured judgment"}],
+        "schedule_planner": [{"type": "plan", "detail": "explicit schedule or priorities"}],
+        "executor": [{"type": "execution", "detail": "tool output or mutation result"}],
+    }
+    return mapping.get(role, [{"type": "summary", "detail": "task summary"}])
+
+
+def _build_rationale(parallel_worthiness: ParallelWorthiness, roles: list[str]) -> str:
+    return (
+        f"preferred_mode={parallel_worthiness.preferred_mode}; "
+        f"score={parallel_worthiness.score:.2f}; "
+        f"roles={','.join(roles)}"
+    )