refactor: unify hub access via MemoryHubDatabase.getDefault() in application layer

- Add MemoryHubDatabase.getDefault() factory that respects test override
- Add MemoryHubDatabase.setTestOverride() synced from MemoryStore.setSharedHubForTests
- getDefault() creates a new connection to the same path (safe to close per-consumer)
- Replace direct new MemoryHubDatabase() in application and monitoring layers
- Eliminates the bypass path that caused ghost project leaks in tests

Author: codefromkarl

src/application/memory/executeAutoRecord.ts

@@ -42,7 +42,7 @@ function resolveProjectRoot(projectId?: string): string {
     return path.resolve(projectId);
   }
 
-  const db = new MemoryHubDatabase();
+  const db = MemoryHubDatabase.getDefault();
   try {
     const project = db.getProject(projectId);
     if (!project?.path) {

src/application/memory/executeMemoryHub.ts

@@ -105,7 +105,7 @@ export async function executeQuerySharedMemories(
     'MCP query_shared_memories 调用开始',
   );
 
-  const db = new MemoryHubDatabase();
+  const db = MemoryHubDatabase.getDefault();
 
   try {
     const normalizedQueryText = buildFtsPrefixQuery(effectiveQuery);
@@ -215,7 +215,7 @@ export async function executeLinkMemories(args: LinkMemoriesInput): Promise<Memo
 
   logger.info({ from, to, type }, 'MCP link_memories 调用开始');
 
-  const db = new MemoryHubDatabase();
+  const db = MemoryHubDatabase.getDefault();
 
   try {
     const fromMemory = db.getMemory(from.project, from.module);
@@ -266,7 +266,7 @@ export async function executeGetDependencyChain(
 
   logger.info({ project, module, recursive }, 'MCP get_dependency_chain 调用开始');
 
-  const db = new MemoryHubDatabase();
+  const db = MemoryHubDatabase.getDefault();
 
   try {
     const memory = db.getMemory(project, module);
@@ -359,7 +359,7 @@ export async function executeGetDependencyChain(
 }
 
 export async function executeManageProjects(args: ManageProjectsInput): Promise<MemoryToolResponse> {
-  const db = new MemoryHubDatabase();
+  const db = MemoryHubDatabase.getDefault();
 
   try {
     switch (args.action) {

src/memory/MemoryHubDatabase.ts

@@ -151,6 +151,33 @@ const REPAIR_PLACEHOLDER_PREFIX = '__cw_repair__';
 export class MemoryHubDatabase {
   private db: Database.Database;
 
+  /**
+   * 测试覆盖实例 — 由 MemoryStore.setSharedHubForTests 同步设置
+   *
+   * 应用层通过 getDefault() 获取 hub 时会自动使用此覆盖实例，
+   * 从而确保测试隔离不需要在每个应用函数中单独处理。
+   */
+  private static testOverride: MemoryHubDatabase | null = null;
+
+  /** 设置测试覆盖（由 MemoryStore.setSharedHubForTests 调用） */
+  static setTestOverride(hub: MemoryHubDatabase | null): void {
+    MemoryHubDatabase.testOverride = hub;
+  }
+
+  /**
+   * 获取默认 hub 实例。
+   *
+   * 在测试环境下，使用测试覆盖实例的路径创建新连接（而非返回同一实例），
+   * 确保消费者可以安全地 close() 自己的连接而不影响其他调用方。
+   * 在生产环境下，等价于 `new MemoryHubDatabase()`。
+   */
+  static getDefault(): MemoryHubDatabase {
+    if (MemoryHubDatabase.testOverride) {
+      return new MemoryHubDatabase(MemoryHubDatabase.testOverride.dbPath);
+    }
+    return new MemoryHubDatabase();
+  }
+
   constructor(dbPath?: string) {
     this.dbPath = dbPath || resolveDefaultHubPath();
     fs.mkdirSync(path.dirname(this.dbPath), { recursive: true });
@@ -159,7 +186,8 @@ export class MemoryHubDatabase {
     this.initializeSchema();
   }
 
-  private dbPath: string;
+  /** 数据库文件路径（getDefault() 需读取以创建同路径新连接） */
+  readonly dbPath: string;
 
   /**
    * 初始化数据库 schema

src/memory/MemoryStore.ts

@@ -42,10 +42,12 @@ export class MemoryStore {
 
   static setSharedHubForTests(hub: MemoryHubDatabase | null): void {
     MemoryStore.sharedHub = hub;
+    MemoryHubDatabase.setTestOverride(hub);
   }
 
   static resetSharedHubForTests(): void {
     MemoryStore.sharedHub = null;
+    MemoryHubDatabase.setTestOverride(null);
   }
 
   private readonly projectRoot: string;

src/monitoring/memoryHealth.ts

@@ -305,7 +305,7 @@ function buildOverallAssessment(report: MemoryHealthReport): void {
 export async function analyzeMemoryHealth(
   options: { projectRoots?: string[]; staleDays?: number; excludeGhostProjects?: boolean } = {},
 ): Promise<MemoryHealthReport> {
-  const hub = new MemoryHubDatabase();
+  const hub = MemoryHubDatabase.getDefault();
   try {
     const allowedProjectRoots = options.projectRoots?.length
       ? new Set(options.projectRoots.map((projectRoot) => path.resolve(projectRoot)))

src/monitoring/opsMetrics.ts

@@ -148,7 +148,7 @@ function parseFeedbackOutcome(summary: string): string | null {
 async function collectProjectStaleRates(
   staleDays?: number,
 ): Promise<Map<string, { projectName: string; staleMemoryRate: number; correctionRate: number }>> {
-  const hub = new MemoryHubDatabase();
+  const hub = MemoryHubDatabase.getDefault();
   try {
     const projects = hub.listProjects();
     const result = new Map<
@@ -207,7 +207,7 @@ async function collectProjectStaleRates(
 async function collectModuleQualityDistribution(
   staleDays?: number,
 ): Promise<OpsMetricsReport['moduleQualityDistribution']> {
-  const hub = new MemoryHubDatabase();
+  const hub = MemoryHubDatabase.getDefault();
   try {
     const projects = hub.listProjects();
     const result: OpsMetricsReport['moduleQualityDistribution'] = [];
@@ -285,7 +285,7 @@ async function collectGovernanceSummary(
     },
   };
 
-  const hub = new MemoryHubDatabase();
+  const hub = MemoryHubDatabase.getDefault();
   try {
     const projects = hub.listProjects();
     for (const project of projects) {