feat(ai): AgentTool trait + ToolRegistry + AgentOrchestrator — ReAct 循环（最多 5 轮 Tool Call）

crates/erp-ai/src/agent/tool.rs

@@ -0,0 +1,55 @@
+use async_trait::async_trait;
+use erp_core::health_provider::HealthDataProvider;
+use sea_orm::DatabaseConnection;
+use serde::{Deserialize, Serialize};
+use std::sync::Arc;
+use uuid::Uuid;
+
+/// Agent Tool trait — 所有 Agent 可调用的工具都实现此 trait
+#[async_trait]
+pub trait AgentTool: Send + Sync {
+    fn name(&self) -> &str;
+    fn description(&self) -> &str;
+    fn parameters_schema(&self) -> serde_json::Value;
+    async fn execute(&self, ctx: &ToolContext, params: serde_json::Value) -> ToolResult;
+}
+
+/// Tool 执行上下文 — 包含安全过滤后的租户/用户信息
+pub struct ToolContext {
+    pub tenant_id: Uuid,
+    pub user_id: Uuid,
+    pub patient_id: Option<Uuid>,
+    pub db: DatabaseConnection,
+    pub health_provider: Arc<dyn HealthDataProvider>,
+}
+
+/// Tool 执行结果
+pub struct ToolResult {
+    pub output: String,
+    pub display_hint: Option<DisplayHint>,
+}
+
+/// 前端渲染提示 — 告诉前端如何富化展示 Tool 返回的数据
+#[derive(Debug, Clone, Serialize, Deserialize)]
+#[serde(tag = "type", rename_all = "snake_case")]
+pub enum DisplayHint {
+    VitalCard {
+        indicator_type: String,
+        values: Vec<(String, f64)>,
+        unit: String,
+    },
+    LabReportCard {
+        report_date: String,
+        abnormal_count: usize,
+    },
+    ActionConfirm {
+        action_type: String,
+        summary: String,
+        confirm_payload: serde_json::Value,
+    },
+    RiskAlert {
+        level: String,
+        message: String,
+    },
+    Text,
+}