fix: user constructor from viewer

[RLesser]

Classes derived from AtlasBaseClass should be initializable using an AtlasViewer. Because AtlasUser overrode the base constructor, we lost the ability to do this. This re-adds the ability to construct an AtlasUser from an AtlasViewer, while preserving the legacy object based initialization.

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:rocket:	This description was created by Ellipsis for commit 1dc5c890bae80f6bccf3ef4451a6aa024482d272

Summary:

This PR updates the AtlasUser constructor to accept an AtlasViewer instance, restoring functionality and adding corresponding tests.

Key points:

• Updated src/user.ts to modify AtlasUser constructor to accept AtlasViewer.
• Preserved legacy initialization using ViewMakerArgs.
• Added test in tests/user.test.js to verify AtlasUser initialization with AtlasViewer.

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Generated with :heart: by ellipsis.dev

[RLesser]

• #69 👈
• main

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