Migrate from Carthage to SPM (RIBs-iOS 1.0)

[srea]

Background

RIBs for iOS has moved to a dedicated repository and modern tooling:

• Old: uber/RIBs 0.9.x + Carthage + RxSwift 5
• Current: uber/RIBs-iOS 1.0.0 + SPM (recommended) + RxSwift 6.x, minimum iOS 15

RIBsTreeViewerClient still uses Carthage (Cartfile pins RIBs 0.9.2) and an outdated Package.swift (points at uber/RIBs master). Carthage requires fragile workarounds on Xcode 15+ / Apple Silicon (patch_carthage_checkouts.sh, --use-xcframeworks).

Goal

Replace Carthage with Swift Package Manager and align with RIBs-iOS 1.0+, while keeping the library usable via prebuilt XCFramework for consumers who do not use SPM.

Phased plan

Phase 1 — SPM manifest & compile check (this issue)

• Update Package.swift: RIBs-iOS 1.0+, RxSwift 6.x, iOS 15+
• Align @available / platform requirements in source
• Verify swift build or Xcode SPM build succeeds
• Document Phase 1 completion in a PR linked to this issue

Phase 2 — Xcode project & CI

• Remove Carthage references from RIBsTreeViewerClient.xcodeproj
• Switch GitHub Actions iOS job from make setup-ci to SPM resolve + xcodebuild
• Keep Carthage paths documented as deprecated until Phase 4

Phase 3 — XCFramework distribution

• Regenerate Products/RIBsTreeViewerClient.xcframework using SPM-resolved dependencies
• Update README integration docs (SPM first, XCFramework second)

Phase 4 — Cleanup

• Remove Cartfile, Cartfile.resolved, Carthage patch scripts, DeploymentTarget.xcconfig
• Simplify Makefile (drop setup / setup-ci Carthage targets)
• Close related Dependabot noise if any remains

Non-goals (for now)

• Swift Concurrency / SwiftUI support in RIBsTreeViewer (future RIBs-iOS direction)
• Breaking API changes to RIBsTreeViewer public surface unless required by RIBs 1.0

References

• https://github.com/uber/RIBs-iOS
• https://github.com/uber/RIBs-iOS/releases/tag/1.0.0
• https://github.com/uber/RIBs (Android; iOS moved out)

[srea]

Phase 1 in progress: PR will be linked below.

Deliverables:

• Package.swift → RIBs-iOS 1.0 + RxSwift 6
• scripts/build-spm-package.sh + CI spm job
• Carthage / Xcode project unchanged until Phase 2

[srea]

Phase 1 merged via #39.

• SPM: RIBs-iOS 1.0.0, RxSwift 6.10.2, iOS 15+
• ./scripts/build-spm-package.sh + CI spm job

Next: Phase 2 — remove Carthage from Xcode project and point the ios CI job at SPM.

[srea]

Phase 2–3 PR: usability verification + SPM Xcode project + XCFramework iOS 15 regeneration. See linked PR.