fix(P2): v0.6.3 原子性/一致性/资源治理 — 8 项修复 + 12 回归

- KVStore 混合写单记录原子：新增 writeBatch（put+delete 同一条日志记录），
  KVStoreEngine 全部混合写路径统一（兑现真原子宣称，崩溃无新旧行并存）
- WAL full 模式写入失败抛错（此前 console.warn 吞错 → 崩溃即丢且无感知）
- MemoryEngine SET NULL 级联索引残留：复用 removeIndexEntries（消除虚假 UNIQUE_VIOLATION）
- delete 级联两阶段：先全量 RESTRICT 预检（沿 CASCADE 链递归）再执行，无部分级联
  （Memory/Aria 对齐）
- BufferPool 驱逐同步清理 pages Map（EvictionManager onRemove 回调，内存预算真实生效）
- MVCC commit 清理已提交版本（版本链仅作事务内 undo，消除行数据双份常驻）
- LSM.flush 重复入链修复（入链即置空 immutable）+ frozenMemtables 可见性时序
- rollbackToSavepoint 重建受影响表二级索引（消除过期索引条目）

测试 1114 → 1126（71 套件）；行覆盖率 89.7%；版本 0.6.3

src/engine/aria/index.ts

@@ -871,6 +871,19 @@ export class AriaEngine implements IStorageEngine {
     // v0.4.1: 外键级联（环路保护）
     const visited = new Set<string>();
 
+    // v0.6.3-fix: 级联两阶段 —— 先对全部匹配行做 RESTRICT 预检（沿 CASCADE 链递归），
+    // 否则第 N 行 RESTRICT 抛错时前 N-1 行的级联已执行 → 无事务部分级联（数据不一致）
+    const matchedPks: string[] = [];
+    for (const row of rows) {
+      if (!query.where || Object.keys(query.where).length === 0 || matchWhere(row, query.where)) {
+        matchedPks.push(String(row[this.tablePKs.get(tableName)!]));
+      }
+    }
+    const restrictVisited = new Set<string>();
+    for (const pkValue of matchedPks) {
+      await this.checkCascadeRestrict(tableName, pkValue, restrictVisited);
+    }
+
     for (const row of rows) {
       const pkCol = this.tablePKs.get(tableName)!;
       const key = `${tableName}:${row[pkCol]}`;
@@ -907,6 +920,39 @@ export class AriaEngine implements IStorageEngine {
     return count;
   }
 
+  /**
+   * v0.6.3: RESTRICT 预检（delete 级联两阶段之一，与 MemoryEngine 对齐）。
+   * 递归沿 CASCADE 链检查引用表：RESTRICT 引用存在依赖行则抛 FOREIGN_KEY_VIOLATION。
+   */
+  private async checkCascadeRestrict(tableName: string, pkValue: string, visited: Set<string>): Promise<void> {
+    const visitKey = `${tableName}:${pkValue}`;
+    if (visited.has(visitKey)) return;
+    visited.add(visitKey);
+
+    for (const [refTableName, refSchema] of this.schemas) {
+      if (refTableName === tableName) continue;
+      for (const [colName, colDef] of Object.entries(refSchema.columns)) {
+        if (!colDef.references || !colDef.onDelete) continue;
+        const [refTable] = colDef.references.split('.');
+        if (refTable !== tableName) continue;
+        const refRows = await this.getAllRows(refTableName);
+        const matched = refRows.filter((r) => String(r[colName]) === pkValue);
+        if (colDef.onDelete === 'RESTRICT' && matched.length > 0) {
+          throw new DatabaseError(
+            `Cannot delete from "${tableName}": foreign key "${colName}" in "${refTableName}" has dependent rows`,
+            'FOREIGN_KEY_VIOLATION',
+          );
+        }
+        if (colDef.onDelete === 'CASCADE') {
+          const refPkCol = this.tablePKs.get(refTableName)!;
+          for (const refRow of matched) {
+            await this.checkCascadeRestrict(refTableName, String(refRow[refPkCol]), visited);
+          }
+        }
+      }
+    }
+  }
+
   /**
    * v0.4.1: 外键级联规则 — 对齐 MemoryEngine.cascadeDelete 行为。
    * 删除 tableName 主键为 pkValue 的行前，检查引用它的所有表：
@@ -1328,6 +1374,15 @@ export class AriaEngine implements IStorageEngine {
   async rollbackToSavepoint(name: string): Promise<void> {
     const sp = this.savepoints.get(name);
     if (!sp) throw new DatabaseError(`Savepoint "${name}" not found`, 'SAVEPOINT_NOT_FOUND');
+    // v0.6.3-fix: 记录当前快照涉及的表（回滚后重建索引）—— 此前事务内直写
+    // 索引 LSM，savepoint 回滚只还原快照 → savepoint 之后的索引条目残留
+    const affectedTables = new Set<string>();
+    if (this.txnSnapshot) {
+      for (const key of this.txnSnapshot.keys()) {
+        const idx = key.indexOf(':');
+        if (idx > 0) affectedTables.add(key.slice(0, idx));
+      }
+    }
     // 恢复到 savepoint 时的快照
     this.txnSnapshot = sp.snapshot ? new Map(sp.snapshot) : null;
     // v0.3.3: 清理该事务在 MVCC 版本链中的全部记录（快照已含正确数据，
@@ -1339,6 +1394,12 @@ export class AriaEngine implements IStorageEngine {
       if (k === name) { found = true; continue; }
       if (found) this.savepoints.delete(k);
     }
+    // v0.6.3-fix: 重建受影响表二级索引（消除 savepoint 之后的过期索引条目）
+    for (const tableName of affectedTables) {
+      if (this.schemas.has(tableName)) {
+        await this.reindexTable(tableName);
+      }
+    }
   }
 
   async releaseSavepoint(name: string): Promise<void> {