feat(aihr): add evidence grading, clarification loop and route exits to ask agent

- narrow amount-semantics clarification to adjudicative intents only
- persist pending clarification on conversation and resolve follow-up
  replies as ANSWERED/GAVE_UP/NEW_TOPIC (max one round per field)
- add AihrEvidenceGradingService: FULL/PARTIAL/GUIDANCE/ROUTE arbitration,
  policy-claim post-validation, reference answers labeled as non-formal
- unblock retrieval source gating; tag citations with evidence tier,
  keep PUBLISHED/HUMAN_VERIFIED/effective-date authorization gates
- replace operator-facing no-evidence copy with actionable route exits
  (human help, direct finance channel, web research)
- allow fragment-less down feedback for own NO_EVIDENCE queries so
  ROUTE answers can escalate to human help (fragment_id nullable)
- migrations: aihr_20260804_pending_clarification_mysql8.sql,
  aihr_20260804_feedback_fragment_nullable_mysql8.sql

backend/script/sql/aihr_knowledge_mysql8.sql

@@ -329,6 +329,7 @@ CREATE TABLE IF NOT EXISTS `aihr_knowledge_conversation` (
   `context_json` json DEFAULT NULL COMMENT '最近六轮脱敏短期上下文',
   `state_version` bigint NOT NULL DEFAULT 0 COMMENT '受约束Agent结构化状态乐观版本',
   `state_json` json DEFAULT NULL COMMENT '受控引用元数据和结构化槽位；不保存工具事实正文',
+  `pending_clarification_json` varchar(1000) DEFAULT NULL COMMENT '挂起的澄清',
   `expires_time` datetime NOT NULL COMMENT '不活跃过期时间',
   `create_time` datetime NOT NULL COMMENT '创建时间',
   `update_time` datetime NOT NULL COMMENT '更新时间',

backend/script/sql/aihr_practice_mysql8.sql

@@ -329,7 +329,7 @@ CREATE TABLE IF NOT EXISTS `aihr_knowledge_answer_feedback` (
   `tenant_id` varchar(20) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci DEFAULT '000000' COMMENT '租户编号',
   `query_text` varchar(1000) NOT NULL COMMENT '问题原文',
   `query_norm` varchar(500) NOT NULL COMMENT '规范化问题',
-  `fragment_id` bigint NOT NULL COMMENT '知识片段ID',
+  `fragment_id` bigint DEFAULT NULL COMMENT '知识片段ID；无依据回答的反馈为空',
   `verdict` varchar(10) NOT NULL COMMENT '反馈: up/down',
   `category` varchar(100) DEFAULT NULL COMMENT '知识分类',
   `position` varchar(80) DEFAULT NULL COMMENT '岗位',

backend/script/sql/update/aihr_20260804_feedback_fragment_nullable_mysql8.sql

@@ -0,0 +1,31 @@
+-- Allow fragment-less answer feedback for zero-citation (NO_EVIDENCE) answers. Additive and
+-- idempotent on MySQL 8: the unique key keeps its definition; NULL fragment rows are deduplicated
+-- in application code because MySQL unique indexes do not deduplicate NULLs.
+
+SET @aihr_feedback_table_exists := (
+  SELECT COUNT(*)
+    FROM information_schema.tables
+   WHERE table_schema = DATABASE()
+     AND table_name = 'aihr_knowledge_answer_feedback'
+);
+
+SET @aihr_feedback_fragment_nullable := (
+  SELECT COUNT(*)
+    FROM information_schema.columns
+   WHERE table_schema = DATABASE()
+     AND table_name = 'aihr_knowledge_answer_feedback'
+     AND column_name = 'fragment_id'
+     AND is_nullable = 'YES'
+);
+SET @aihr_feedback_fragment_ddl := IF(
+  @aihr_feedback_table_exists = 1 AND @aihr_feedback_fragment_nullable = 0,
+  'ALTER TABLE `aihr_knowledge_answer_feedback` MODIFY COLUMN `fragment_id` bigint DEFAULT NULL COMMENT ''知识片段ID；无依据回答的反馈为空''',
+  'SELECT 1'
+);
+PREPARE aihr_feedback_fragment_stmt FROM @aihr_feedback_fragment_ddl;
+EXECUTE aihr_feedback_fragment_stmt;
+DEALLOCATE PREPARE aihr_feedback_fragment_stmt;
+
+SET @aihr_feedback_table_exists := NULL;
+SET @aihr_feedback_fragment_nullable := NULL;
+SET @aihr_feedback_fragment_ddl := NULL;

backend/script/sql/update/aihr_20260804_pending_clarification_mysql8.sql

@@ -0,0 +1,30 @@
+-- Pending clarification state for the knowledge Q&A clarification loop. Additive and idempotent on MySQL 8.
+-- The conversation row keeps at most one suspended clarification; it is resolved (answered,
+-- given up or replaced by a new topic) on the next turn and never survives the 30-minute expiry.
+
+SET @aihr_pending_conversation_exists := (
+  SELECT COUNT(*)
+    FROM information_schema.tables
+   WHERE table_schema = DATABASE()
+     AND table_name = 'aihr_knowledge_conversation'
+);
+
+SET @aihr_pending_clarification_exists := (
+  SELECT COUNT(*)
+    FROM information_schema.columns
+   WHERE table_schema = DATABASE()
+     AND table_name = 'aihr_knowledge_conversation'
+     AND column_name = 'pending_clarification_json'
+);
+SET @aihr_pending_clarification_ddl := IF(
+  @aihr_pending_conversation_exists = 1 AND @aihr_pending_clarification_exists = 0,
+  'ALTER TABLE `aihr_knowledge_conversation` ADD COLUMN `pending_clarification_json` varchar(1000) DEFAULT NULL COMMENT ''挂起的澄清'' AFTER `state_json`',
+  'SELECT 1'
+);
+PREPARE aihr_pending_clarification_stmt FROM @aihr_pending_clarification_ddl;
+EXECUTE aihr_pending_clarification_stmt;
+DEALLOCATE PREPARE aihr_pending_clarification_stmt;
+
+SET @aihr_pending_conversation_exists := NULL;
+SET @aihr_pending_clarification_exists := NULL;
+SET @aihr_pending_clarification_ddl := NULL;