fix(pkg): no-op install script so npm doesn't inject node-gyp rebuild

[ShawnChen-Sirius]

npm install chdb fails for both published versions (3.0.0 and 3.1.0-rc.1):

node-gyp rebuild  →  no binding.gyp / no C++ sources in the tarball  →  install aborts

Cause

The native addon ships as prebuilt per-platform subpackages (@chdb/lib-<platform>, pulled via optionalDependencies, resolved at runtime by dist/loader.js) — nothing is built on the user's machine. But the repo keeps a binding.gyp for dev builds, and npm auto-injects "install": "node-gyp rebuild" into a published package when it sees a binding.gyp and no explicit install script (the string is never in our source — git log -S finds it nowhere). The files whitelist ships no binding.gyp or sources, so that injected rebuild has nothing to build and the install fails.

Fix

Add an explicit no-op install (node -e "") so npm stops injecting the default. Users get the addon from the subpackage; dev still builds via npm run build.

Verified with npm pack: the tarball's install is now the no-op and binding.gyp is absent.

Follow-ups (not in this PR)

• The already-published 3.0.0 / 3.1.0-rc.1 are immutable; they need patch republishes (3.0.1 / 3.1.0-rc.2) carrying this fix to become installable.
• The publish CI never installs the published package from the registry — adding a clean-room "npm install the packed tarball" check would have caught this.