Add FastAPI backend with agent system

backend/app/agents/state.py

@@ -0,0 +1,105 @@
+from dataclasses import dataclass
+from typing import TypedDict, Annotated
+from enum import Enum
+
+
+class AgentRole(str, Enum):
+    MASTER = "master"
+    PLANNER = "planner"
+    EXECUTOR = "executor"
+    LIBRARIAN = "librarian"
+    ANALYST = "analyst"
+
+
+@dataclass
+class AgentInfo:
+    name: str
+    role: AgentRole
+    description: str
+
+
+@dataclass
+class ToolCall:
+    tool: str
+    args: dict
+    result: str | None = None
+
+
+@dataclass
+class ConversationTurn:
+    role: str  # "user" | "assistant"
+    content: str
+    agent: AgentRole | None = None
+    model: str | None = None
+
+
+def turn_to_message(turn: ConversationTurn) -> HumanMessage:
+    return HumanMessage(content=turn.content)
+
+
+def message_to_turn(msg, agent: AgentRole | None = None) -> ConversationTurn:
+    msg_type = getattr(msg, "type", None) or getattr(msg, "role", "assistant")
+    return ConversationTurn(
+        role="user" if msg_type in ("human", "user") else "assistant",
+        content=msg.content,
+        agent=agent,
+        model=getattr(msg, "model", None),
+    )
+
+
+class AgentState(TypedDict):
+    messages: Annotated[list, None]
+    user_id: str
+    conversation_id: str
+
+    # Agent routing
+    current_agent: AgentRole
+    active_agents: list[AgentRole]
+
+    # Task tracking
+    pending_tasks: list[dict]
+    completed_tasks: list[dict]
+
+    # Tool usage
+    tool_calls: list[ToolCall]
+    last_tool_result: str | None
+
+    # Knowledge context
+    knowledge_context: str | None
+    graph_context: str | None
+
+    # Planning
+    plan: str | None
+    plan_steps: list[dict]
+
+    # Analysis
+    analysis_report: str | None
+
+    # Output control
+    final_response: str | None
+    should_respond: bool
+
+    # Memory context (injected at start of each conversation)
+    memory_context: str | None
+
+
+def initial_state(user_id: str, conversation_id: str) -> AgentState:
+    return AgentState(
+        messages=[],
+        user_id=user_id,
+        conversation_id=conversation_id,
+        current_agent=AgentRole.MASTER,
+        active_agents=[AgentRole.MASTER],
+        pending_tasks=[],
+        completed_tasks=[],
+        tool_calls=[],
+        last_tool_result=None,
+        knowledge_context=None,
+        graph_context=None,
+        plan=None,
+        plan_steps=[],
+        analysis_report=None,
+        final_response=None,
+        should_respond=True,
+        memory_context=None,
+    )