[FSSDK-13238] ci: publish releases automatically when SDKVersion.swift changes

[muzahidul-opti]

Summary

Replaces the manual PREP/RELEASE workflow_dispatch jobs (hub scripts on macOS runners, version in swift.yml) with a release that publishes on merge. SDKVersion.swift is the single source of the version — it's what the SDK reports at runtime (client_version, OptimizelyClient.version), so the tag can't drift from it.

- edit VERSION in swift.yml → PR → run PREP=true → merge bot PR → run RELEASE=true
+ PR: bump SDKVersion.swift + CHANGELOG.md → merge → release.yml tags + publishes

release.yml  (push to master | release/**, paths: Sources/Utils/SDKVersion.swift)
  read OPTIMIZELYSDKVERSION
  tag vX.Y.Z exists?           → exit 0 (safe to re-run)
  CHANGELOG "## X.Y.Z" missing → fail, nothing tagged
  gh release create vX.Y.Z --target $GITHUB_SHA --notes-file <CHANGELOG section>
    -suffix version   → --prerelease
    from release/**   → --latest=false

• swift.yml:
  • drop PREP/RELEASE inputs, VERSION env, per-job if: guards and the two release jobs
  • run CI on release/** too
  • skip integration_tests on manual runs (the ci-helper-tools trigger script rejects workflow_dispatch; the old guards used to skip it)
• run_unit_tests.sh: remove the BRANCH == master guard, which made unit tests report success without running on any other branch.
• Delete run_prep.sh, run_release.sh, update_version.sh, build_all.sh (only used by prep).
• Docs:
  • CLAUDE.md release process: 2 files to bump, release/X.Y.x patch flow, what happens after merge
  • constitution: version files are SDKVersion.swift and CHANGELOG.md; README no longer has a version since the CocoaPods line was removed in [FSSDK-11920] Migrate Swift SDK distribution, CI, and releases to SPM on Xcode 27 #658
  • SDKVersion.swift comment

Test plan

Publish script run locally against the repo:

• Existing tag: version 5.5.0 → tag exists -> skip
• Notes extraction: ## 5.5.0 → 8 lines, ## 5.4.2 → 9 lines, ## 9.9.9 → 0 lines (job fails)
• Flags:

  5.6.0      on master        → (none)
  5.6.0      on release/5.4.x → --latest=false
  5.6.0-beta on master        → --prerelease
  5.6.0-beta on release/5.4.x → --prerelease --latest=false
  

• actionlint clean on release.yml.
• Repo settings: checked that no tag rulesets block GITHUB_TOKEN from creating v* tags. The only rulesets are branch rules (force-push, Arnica).
• Not yet run end-to-end: the publish step runs on the next real release merge. A personal-fork dry run is possible before that.

Merge Danger

Door: two-way. Reverting restores the old jobs and scripts. Once immutable releases are enabled, a published tag can't be moved or reused.
Blast Radius:

• Any merged change to SDKVersion.swift on master/release/** now publishes a release.
• Manual PREP/RELEASE runs no longer exist.
• Unit tests now run for PRs into release/** (previously skipped).
• Recommended settings after merge: branch protection for release/**, immutable releases.

Issues

• FSSDK-13238

🤖 Generated with Claude Code

[coveralls]

coverage: 93.929%. remained the same — muzahid/spm-release-workflow into master

[jaeopt]

LGTM