[100mango]

Summary

• Add the SwiftTimer SwiftPM library, preserving its public API, Swift 5 language mode, Carthage/Xcode integration, and historical platform declarations.
• Expand package coverage to 29 XCTest cases: timer lifecycle and capture release; manual/scheduled firing; handler/interval changes; countdown zero/negative, reset, suspend/resume and callback release; queue selection; debounce/throttle cancellation, reentrancy, and concurrent same/different identifiers; interval conversion boundaries.
• Fix two verified regressions: reentrant throttle registrations were ignored, and reentrant debounce registrations were removed by the previous handler's cleanup. A tokenized, locked private registry now claims pending work before invoking user code, with cancellation and user callbacks outside the lock.
• Document version-based SwiftPM installation starting at 1.2.0, and queue/cancellation semantics.
• Run minimal read-only macos-15 debug/release CI on PRs and master pushes. Checkout does not persist credentials; timeout is 15 minutes, without secrets, signing, uploads, or deployment steps.

Verification

Final PR head: d681bdad5f06ccbbac77b7282412c408e3723930.

• Linux, official Swift 6.4.1: debug 29/29 and release 29/29 passed.
• Focused concurrency/reentrancy tests passed five consecutive Linux runs.
• Both new reentrant regressions failed against the old implementation, then passed after the fix.
• Independent code review found no blocker; an isolated 29-test run passed.
• macOS CI run 40100760271: debug and release passed on the final head.
• git diff --check passed.

iOS, tvOS, watchOS, device builds, and the original Xcode iOS suite have not been run. Modern macOS/Linux results do not establish every historical deployment target. Existing platform declarations remain unchanged.

Release verification

Merged as a4823a86f4304650c4df8e4df1ae38717256ebed; master CI run 40101015058 passed debug and release with 29 tests each.

Release 1.2.0 is published, not a draft or prerelease. Its tag points exactly to the merge commit; existing tags were not overwritten.

A separate consumer fetched https://github.com/100mango/SwiftTimer.git with exact version 1.2.0, resolved that same merge revision, built in release mode, and passed 2 debug plus 2 release integration tests, including the reentrant-throttle fix.