[Bug]: filesystem重写snapshotSpec不生效

**Describe the bug**
filesystem重写snapshotSpec不生效
SandboxFilesystemSpec子类实现
public SandboxFilesystemSpec snapshotSpec(SandboxSnapshotSpec snapshotSpec) {
this.snapshotSpecOverride = snapshotSpec;
return this;
}
方法时，没有重写snapshotSpecOverride，
agent又使用原distributedStore覆盖snapshotSpec
sandboxFilesystemSpec.snapshotSpec(distributedStore.sandboxSnapshotSpec());

我使用redisDistributedStore+LocalSnapshotSpec，快照被存在了redis上
filesystem.image("alpine:3.20")
.workspaceRoot(SANDBOX_WORKSPACE_ROOT)
.memorySizeBytes(SANDBOX_MEMORY_LIMIT_BYTES)
.cpuCount(SANDBOX_CPU_COUNT)
.network("bridge")
.isolationScope(IsolationScope.USER)
.snapshotSpec(new LocalSnapshotSpec(required(
"agentscope.sandbox.snapshot-path", sandboxSnapshotPath)));