feat: treat "null" strings as null

[Swiftwork]

Requires: https://github.com/bucketco/bucket-realtime/pull/510

[Copilot]

Pull Request Overview

This PR updates the flag evaluation logic to treat the string "null" as equivalent to an actual null value in SET and NOT_SET operations. The change is implemented in the flag-evaluation package and propagated through version bumps across dependent packages.

• Modified SET and NOT_SET operations to handle "null" strings as null values
• Bumped package versions to reflect the changes across the dependency chain

Reviewed Changes

Copilot reviewed 4 out of 5 changed files in this pull request and generated 2 comments.

File	Description
packages/flag-evaluation/src/index.ts	Updated SET/NOT_SET logic to treat "null" strings as null values
packages/flag-evaluation/package.json	Version bump to 0.2.2
packages/node-sdk/package.json	Version bump to 1.9.4 and dependency update
packages/openfeature-node-provider/package.json	Dependency update to use new node-sdk version