chore: bump version to 1.0.0-rc.1

[Aqu1tain]

Summary

Prepare release candidate 1.0.0-rc.1

• Update package.json version to 1.0.0-rc.1
• Update CHANGELOG with release date

Release workflow

1. Merge this PR to dev
2. Tag v1.0.0-rc.1 on dev
3. Publish to npm with --tag next
4. After validation, merge dev → main and release 1.0.0

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