chore: Remove misplaced claude .md file (invoke-ai#9315)

## Summary

There was a Claude .md file (USER_ISOLATION_IMPLEMENTATION.md)
inadvertently checked into main. This removes it.

## Related Issues / Discussions

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## QA Instructions

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## Merge Plan

Simple merge

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## Checklist

- [X] _The PR has a short but descriptive title, suitable for a
changelog_
- [ ] _Tests added / updated (if applicable)_
- [ ] _❗Changes to a redux slice have a corresponding migration_
- [ ] _Documentation added / updated (if applicable)_
- [ ] _Updated `What's New` copy (if doing a release after this PR)_

Author: joshistoast