Tag v1.1.0 and publish to SwiftPM registry

[nficano]

No GitHub releases yet; version is 0.1.0-dev. Once features land:

1. Bump version in Package.swift (if version is read from it) or release notes
2. gh release create v1.1.0 --generate-notes
3. If SwiftPM registry is in use, push artifacts there
4. Verify external consumers can swift package add via tag

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Audit reference: ARCP SDK Audit v1.1 (2026-05-19)