feat(aihr): add grounded agent shadow runtime

backend/script/sql/update/aihr_20260804_grounded_agent_state_mysql8.sql

@@ -0,0 +1,46 @@
+-- Grounded Agent structured conversation state. Additive and idempotent on MySQL 8.
+-- Legacy context_json remains the unchanged List<Turn> contract.
+
+SET @aihr_agent_conversation_exists := (
+  SELECT COUNT(*)
+    FROM information_schema.tables
+   WHERE table_schema = DATABASE()
+     AND table_name = 'aihr_knowledge_conversation'
+);
+
+SET @aihr_agent_state_version_exists := (
+  SELECT COUNT(*)
+    FROM information_schema.columns
+   WHERE table_schema = DATABASE()
+     AND table_name = 'aihr_knowledge_conversation'
+     AND column_name = 'state_version'
+);
+SET @aihr_agent_state_ddl := IF(
+  @aihr_agent_conversation_exists = 1 AND @aihr_agent_state_version_exists = 0,
+  'ALTER TABLE `aihr_knowledge_conversation` ADD COLUMN `state_version` bigint NOT NULL DEFAULT 0 COMMENT ''受约束Agent结构化状态乐观版本'' AFTER `context_json`',
+  'SELECT 1'
+);
+PREPARE aihr_agent_state_stmt FROM @aihr_agent_state_ddl;
+EXECUTE aihr_agent_state_stmt;
+DEALLOCATE PREPARE aihr_agent_state_stmt;
+
+SET @aihr_agent_state_json_exists := (
+  SELECT COUNT(*)
+    FROM information_schema.columns
+   WHERE table_schema = DATABASE()
+     AND table_name = 'aihr_knowledge_conversation'
+     AND column_name = 'state_json'
+);
+SET @aihr_agent_state_ddl := IF(
+  @aihr_agent_conversation_exists = 1 AND @aihr_agent_state_json_exists = 0,
+  'ALTER TABLE `aihr_knowledge_conversation` ADD COLUMN `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'' AFTER `state_version`',
+  'SELECT 1'
+);
+PREPARE aihr_agent_state_stmt FROM @aihr_agent_state_ddl;
+EXECUTE aihr_agent_state_stmt;
+DEALLOCATE PREPARE aihr_agent_state_stmt;
+
+SET @aihr_agent_conversation_exists := NULL;
+SET @aihr_agent_state_version_exists := NULL;
+SET @aihr_agent_state_json_exists := NULL;
+SET @aihr_agent_state_ddl := NULL;