FN-6312: stabilize checkout leasing AgentStore test

Stabilize the checkout leasing AgentStore regression test setup.

- Recreate the nested checkout-leasing AgentStore with an in-memory database after replacing the TaskStore.
- Keep the disk-backed TaskStore for persistence assertions while avoiding a shared disk-backed AgentStore database lifecycle.
- Let the top-level cleanup own AgentStore closure to avoid double-closing in the nested hook.

Files changed:
 packages/core/src/__tests__/agent-store.test.ts | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

Fusion-Task-Id: FN-6312
Fusion-Task-Lineage: a7f95ba4-fe8b-4367-9f65-6696b1a3867a

packages/core/src/__tests__/agent-store.test.ts

@@ -1846,7 +1846,11 @@ describe("AgentStore", () => {
       taskStore = new TaskStore(rootDir, join(rootDir, ".fusion-global-settings"));
       await taskStore.init();
 
-      store = new AgentStore({ rootDir, taskStore });
+      // Mirror the top-level AgentStore setup: checkout-leasing assertions need
+      // the disk-backed TaskStore for task persistence, but not a disk-backed
+      // AgentStore SQLite database in a shared hook.
+      store.close();
+      store = new AgentStore({ rootDir, inMemoryDb: true, taskStore });
       await store.init();
 
       const holder = await store.createAgent({ name: "Checkout Holder", role: "executor" });
@@ -1859,7 +1863,6 @@ describe("AgentStore", () => {
     });
 
     afterEach(() => {
-      store.close();
       taskStore.close();
     });