feat(firstleg): enforce single remainder split schema

firstleg/src/test/java/com/baiyue/firstleg/repository/InboundParentChildSqlContractTest.java

@@ -22,10 +22,13 @@ class InboundParentChildSqlContractTest {
             .contains("'fl_inbound_order', 'package_count'")
             .contains("'fl_inbound_order', 'split_purpose'")
             .contains("SET split_purpose = 'REMAINDER'")
+            .contains("active_remainder_root_id")
             .contains("GENERATED ALWAYS AS (CASE WHEN inbound_role = 'MASTER'")
+            .contains("GENERATED ALWAYS AS (CASE WHEN inbound_role = 'CHILD'")
             .contains("DROP INDEX uk_inbound_tenant_order")
             .contains("uk_inbound_master_order")
             .contains("uk_inbound_parent_split_sequence")
+            .contains("uk_inbound_one_active_remainder")
             .contains("DROP INDEX uk_inbound_parent_sequence");
     }
 
@@ -54,17 +57,23 @@ class InboundParentChildSqlContractTest {
     }
 
     @Test
-    void protectsOwnershipAndTotals() {
+    void protectsSingleRemainderWritesAndConservation() {
         assertThat(sql)
             .contains("子入仓单必须绑定同一客户的有效主单")
             .contains("parent_order.version > NEW.expected_parent_version")
             .contains("NEW.loaded_package_count")
             .contains("NEW.remaining_package_count")
             .contains("NEW.loaded_package_count + NEW.remaining_package_count <> NEW.package_count")
+            .contains("NEW.loaded_child_inbound_id IS NOT NULL")
+            .contains("NEW.child_inbound_id = batch.remainder_child_inbound_id")
+            .contains("source_order.package_count = NEW.loaded_package_count")
+            .contains("item.child_inbound_id <> NEW.remainder_child_inbound_id")
+            .contains("<> NEW.remaining_package_count")
+            .contains("根入仓单原始箱数与已完成分片及当前余量不守恒")
             .contains("COALESCE(source_order.package_count, source_order.total_package_count) = NEW.package_count")
             .contains("AND plan_item.deleted = 0))))\n       OR NOT EXISTS (")
             .contains("source_batch.inbound_id = COALESCE(batch.source_inbound_id, batch.parent_inbound_id)")
-            .contains("拆分批次来源必须是箱数匹配且未消费的根主单或余量子单")
+            .contains("拆分批次来源必须是箱数守恒的根主单或余量分片")
             .contains("SUM(split_item.package_count) > source_item.package_count")
             .contains("子单承接箱数超过来源测量箱规箱数")
             .contains("child_order.package_count >= NEW.package_count")
@@ -75,13 +84,14 @@ class InboundParentChildSqlContractTest {
     }
 
     @Test
-    void validatesMultiChildAndMultiSkuTotals() {
+    void validatesSingleRemainderAndMultiSkuTotals() {
         assertThat(sql)
             .contains("uk_inbound_parent_split_sequence")
+            .contains("uk_inbound_one_active_remainder")
             .contains("uk_inbound_split_batch_line")
             .contains("uk_inbound_split_batch_source_child")
             .contains("COUNT(DISTINCT item.child_inbound_id)")
-            .contains("NOT BETWEEN 1 AND 2")
+            .contains("<> CASE WHEN NEW.remaining_package_count > 0 THEN 1 ELSE 0 END")
             .contains("child_order.package_count <> SUM(item.package_count)");
     }
 
@@ -108,6 +118,7 @@ class InboundParentChildSqlContractTest {
         assertThat(sql)
             .contains("table_name = 'fl_inbound_split_batch'")
             .contains("uk_inbound_split_source_once")
+            .contains("uk_inbound_one_active_remainder")
             .contains("table_name = 'fl_inbound_split_item'")
             .contains("uk_inbound_split_batch_source_child")
             .contains("is_nullable = 'NO'")

firstleg/src/test/java/com/baiyue/firstleg/repository/Phase3FinalUnifiedSqlContractTest.java

@@ -107,6 +107,22 @@ class Phase3FinalUnifiedSqlContractTest {
             .doesNotContain("UNIQUE KEY `uk_inbound_split_batch_source_item`");
     }
 
+    @Test
+    void unifiedEntryEnforcesSingleRemainderWritesAndKeepsLegacyColumns() throws Exception {
+        String sql = normalise(Files.readString(resolveUnified()));
+
+        assertThat(sql)
+            .contains("'fl_inbound_order', 'active_remainder_root_id'")
+            .contains("uk_inbound_one_active_remainder")
+            .contains("uk_inbound_split_source_once")
+            .contains("NEW.loaded_child_inbound_id IS NOT NULL")
+            .contains("NEW.child_inbound_id = batch.remainder_child_inbound_id")
+            .contains("source_order.package_count = NEW.loaded_package_count")
+            .contains("根入仓单原始箱数与已完成分片及当前余量不守恒")
+            .contains("'fl_inbound_split_batch', 'loaded_child_inbound_id'")
+            .contains("fk_inbound_split_loaded_child");
+    }
+
     private static void assertBlock(String unified, String marker, String nextMarker, String modulePath)
         throws Exception {
         int start = unified.indexOf(marker);

firstleg/src/test/java/com/baiyue/firstleg/split/service/SplitPreloadSqlContractTest.java

@@ -16,7 +16,7 @@ class SplitPreloadSqlContractTest {
     }
 
     @Test
-    void limitsSecondaryInboundDepth() throws Exception {
+    void limitsNewChildrenToRootBasedRemainders() throws Exception {
         String sql = moduleMigration();
         assertThat(sql)
             .contains("parent_inbound_id")
@@ -25,7 +25,8 @@ class SplitPreloadSqlContractTest {
             .contains("split_status")
             .contains("uk_inbound_parent_split_sequence")
             .contains("fk_inbound_parent_order")
-            .contains("子入仓单必须标记LOADED或REMAINDER")
+            .contains("新建子入仓单只能作为余量分片")
+            .contains("uk_inbound_one_active_remainder")
             .contains("入仓单主子归属创建后不可修改");
     }