Add comprehensive test coverage and CI workflow

[anthony1810]

Summary

• Add comprehensive test coverage with 43 tests across 10 test suites
• Add GitHub Actions CI workflow for automated testing on PRs to main
• Add Sendable conformance to BindingParentStateOption for Swift 6 compatibility
• Add README badges (Swift, iOS, macOS, Tests, Fully Tested)
• Refactor integration tests to use makeSUT factory methods with memory leak tracking

Test Coverage

• ActionLocker, ActionLockable, AsyncAction
• ScreenState, LoadmoreScreenStates
• StreamProducer, AnyAsyncStream, CancelBag
• StateKeyPathUpdatable
• Store/State integration tests

Test plan

• All 43 tests pass locally
• CI workflow configured for PRs to main