fix: declare apache-arrow as a direct runtime dependency

[sd1114820]

Summary

Declare apache-arrow as a direct runtime dependency of memory-lancedb-pro.

Why

@lancedb/lancedb requires apache-arrow at runtime, but currently exposes it via peerDependencies.
That works in some regular npm environments, but it can be missed by isolated plugin installation flows.

One reproducible case is OpenClaw's plugin installer, which installs plugin dependencies with:

npm install --omit=dev --omit=peer --ignore-scripts

In that environment, apache-arrow is not installed, and the plugin later fails when LanceDB is loaded:

memory-lancedb-pro: failed to load LanceDB
Cannot find module 'apache-arrow'

Declaring apache-arrow directly fixes both:

• regular npm installation
• isolated OpenClaw plugin installation

Changes

• add apache-arrow@18.1.0 to dependencies
• add a regression assertion so the package keeps declaring it directly
• refresh package-lock.json

Verification

Ran in a clean container:

npm ci
node test/plugin-manifest-regression.mjs
node --test test/sync-plugin-version.test.mjs

All passed.

[rwmjhb]

感谢这个聚焦修复。

我这边复现了 --omit=peer 安装路径下缺少 apache-arrow 导致 LanceDB 运行时加载失败的问题；把它声明为直接依赖可以把这个缺口补上。

本地已在隔离目录上应用 PR 补丁并跑完整 npm test，全部通过。现在执行合并。

[rwmjhb]

Thanks for the focused fix.

I reproduced the runtime failure when installs omit peer dependencies, and declaring apache-arrow directly closes that gap cleanly. Merging this now.