[FSSDK-11920] Migrate Swift SDK distribution, CI, and releases to SPM on Xcode 27

[Copilot]

Summary

• Packaging: remove CocoaPods (podspecs, Podfile, Pods refs) and the stale Carthage README badge/install section (Carthage support was dropped earlier), making Swift Package Manager the only supported distribution path
• Platform minimums: raise to Xcode 27's supported floors: iOS 15.0 / tvOS 15.0 / watchOS 9.0 / macOS 12.0, in Package.swift, the SDK xcodeproj, and the demo app
• Workspace: keep OptimizelySwiftSDK.xcworkspace so the SDK and demo targets open together, minus the dead Pods/podspec references
• Demo app: remove CocoaPods (xcconfigs, framework links, manifest-lock phases); the lint phase calls a Homebrew-installed swiftlint and skips with a warning if it's missing. Move iOS/tvOS to the UIScene life cycle (SceneDelegate + UIApplicationSceneManifest), which apps built with the iOS/tvOS 27 SDK require or they crash at launch
• CI: package-native validation (swift package resolve / swift build) and a simulator matrix on xcode-27 run directly from OptimizelySwiftSDK.xcodeproj: iPhone 17, iPad Pro 11-inch (M5), iPhone Air, Apple TV 4K (3rd gen), all OS 27.0. unittests calls the local ./.github/workflows/unit_tests.yml, so PRs test their own workflow changes
• CI fixes: quote the matrix os: "27.0" (YAML parsed it as float 27); replace iPhone 17 Pro, which the runner image doesn't have; retry the unit-test step up to 3 times, because a few async-ordering tests (e.g. testDecideAsyncCompletionOrder) fail at random; name the test step; drop the unused coveralls-lcov gem
• Release automation: stop updating/publishing podspecs; release prep updates SDK source versioning only, and release jobs publish GitHub releases only
• Coverage: pin xccov2lcov to a commit and coverallsapp/github-action to v2 (both were floating), and mark the coverage steps continue-on-error so a coverage failure can't fail the test job
• Cleanup: delete orphaned Scripts/prepare_simulator.sh, Scripts/runtimeVersion.sh and Scripts/change_header/replace_headers_folder.sh, drop the CocoaPods section from .gitignore, and update README / CONTRIBUTING / CLAUDE.md for an SPM-only workflow with the new minimums

CocoaPods support is being sunset and the CI runners now use Xcode 27, which can't build for targets below iOS 15 / tvOS 15 / watchOS 9 / macOS 12. Breaking for consumers: CocoaPods installs are gone, and the minimum OS versions go up (iOS 15 / tvOS 15 / watchOS 9 / macOS 12). This needs a major release (6.0.0). CHANGELOG and VERSION in swift.yml are updated in the release PR; that entry should call out both the removed CocoaPods support and the new minimums, and note that 5.5.0 is the last version available via CocoaPods.

Test plan

• swift package dump-package passes; plutil -lint and xcodebuild -list pass for OptimizelySwiftSDK.xcodeproj and DemoSwiftApp.xcodeproj
• Built and launched DemoSwiftiOS on an iOS 27 simulator: no UIScene launch crash, splash screen renders, process stays alive
• CI unit-test matrix runs from this branch's workflow on xcode-27. The retry loop covers the known flaky tests; they are not fixed in this PR
• FSC with this branch plus swift-testapp#146 (FSC run 36562708439): the testapp resolved swift-sdk @ copilot/remove-cocoapod-support through SPM and built, and the IPA was uploaded to BrowserStack
• tvOS/watchOS demo targets have not been run

Issues

• FSSDK-11920

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[datadog-optimizely-experimentation]

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[muzahidul-opti]

@copilot @claude review the pr

[Copilot]

@copilot @claude review the pr

Reviewed and addressed the follow-ups in a21ef42: removed the invalid retries key by using a shell retry loop, switched swift.yml back to the same-repo reusable unit_tests.yml, and lowered Package.swift to tools-version 5.3 while keeping the watchOS 9.0 floor. Revalidated the workflows/package metadata and the final Actions/CodeQL validation came back clean.

[coveralls]

coverage: 93.929%. remained the same — copilot/remove-cocoapod-support into master

[jaeopt]

Critical issues

1. The version and CHANGELOG don't reflect the breaking change.

• This PR removes CocoaPods and raises the minimum iOS from 10 to 15, which breaks existing consumers. Under semver, that needs a major version (6.0.0), not 5.6.0.
• CHANGELOG.md isn't touched. Its top entry is still 5.5.0.
• .github/workflows/swift.yml still has VERSION: 5.5.0.

2. Carthage support is also removed, and the PR doesn't mention it.
The README removes the Carthage badge and its whole install section, but the PR description only covers CocoaPods. The CHANGELOG and README should tell both groups of users how to migrate, for example: "5.5.0 is the last version available via CocoaPods/Carthage; use Swift Package Manager going forward."

[muzahidul-opti]

Thanks @jaeopt.

1. CHANGELOG and VERSION are updated in the release PR per our usual process. I've fixed the PR description to say this needs a major release (6.0.0) and listed what the entry must cover.
2. Carthage support was dropped a while ago. This PR only removes the stale README badge and install section. I've clarified that in the description, so no Carthage migration note is needed.

🤖 Generated with Claude Code

[jaeopt]

LGTM - I see we need to upgrade to v6 when we release it.