test(ai): erp-ai 从零增至 34 个单元测试 — 覆盖 DTO/error/prompt/sanitization

- dto.rs: 8 个测试（AnalysisType 映射、serde round-trip、SSE 事件、默认值）
- error.rs: 10 个测试（AiError 全部 10 个变体 → AppError 映射）
- prompt: 8 个测试（变量替换、嵌套对象、数组迭代、条件、严格模式缺失变量）
- sanitization: 8 个测试（4 种 DTO 脱敏通过、PII 字段检测、空数据边界）

crates/erp-ai/src/prompt/mod.rs

@@ -23,3 +23,86 @@ impl PromptRenderer {
             .map_err(|e| AiError::TemplateError(format!("模板渲染失败: {e}")))
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use serde_json::json;
+
+    fn renderer() -> PromptRenderer {
+        PromptRenderer::new()
+    }
+
+    #[test]
+    fn render_simple_variable() {
+        let r = renderer();
+        let result = r.render("你好 {{name}}", &json!({"name": "患者"})).unwrap();
+        assert_eq!(result, "你好 患者");
+    }
+
+    #[test]
+    fn render_multiple_variables() {
+        let r = renderer();
+        let result = r.render(
+            "{{age_group}} {{sex}} 化验报告",
+            &json!({"age_group": "中年", "sex": "男性"}),
+        )
+        .unwrap();
+        assert_eq!(result, "中年 男性 化验报告");
+    }
+
+    #[test]
+    fn render_with_nested_object() {
+        let r = renderer();
+        let data = json!({
+            "report": { "date": "2026-05-01", "department": "内科" }
+        });
+        let result = r.render("科室: {{report.department}}，日期: {{report.date}}", &data).unwrap();
+        assert_eq!(result, "科室: 内科，日期: 2026-05-01");
+    }
+
+    #[test]
+    fn render_with_array_iteration() {
+        let r = renderer();
+        let data = json!({"items": ["WBC", "HGB", "PLT"]});
+        let result = r.render("指标: {{#each items}}{{this}}, {{/each}}", &data).unwrap();
+        assert_eq!(result, "指标: WBC, HGB, PLT, ");
+    }
+
+    #[test]
+    fn render_missing_variable_in_strict_mode_errors() {
+        let r = renderer();
+        let result = r.render("你好 {{missing_var}}", &json!({}));
+        assert!(result.is_err());
+        match result.unwrap_err() {
+            AiError::TemplateError(msg) => assert!(msg.contains("missing_var")),
+            other => panic!("期望 TemplateError，得到 {:?}", other),
+        }
+    }
+
+    #[test]
+    fn render_empty_template() {
+        let r = renderer();
+        let result = r.render("", &json!({})).unwrap();
+        assert_eq!(result, "");
+    }
+
+    #[test]
+    fn render_template_with_no_variables() {
+        let r = renderer();
+        let result = r.render("这是一段固定文本", &json!({})).unwrap();
+        assert_eq!(result, "这是一段固定文本");
+    }
+
+    #[test]
+    fn render_with_conditional() {
+        let r = renderer();
+        let data = json!({"is_abnormal": true, "value": "偏高"});
+        let result = r.render(
+            "{{#if is_abnormal}}异常: {{value}}{{else}}正常{{/if}}",
+            &data,
+        )
+        .unwrap();
+        assert_eq!(result, "异常: 偏高");
+    }
+}