[rinekri]

Adds the Scheduler helpers that apps currently copy locally. Additive only.

• startIfIdle(handle, argument, tag) / startIfIdle(handle): atomic check+start, returns JobHandle? (null if dropped)
• startSuspendedIfIdle(handle, argument, tag) / startSuspendedIfIdle(handle): startSuspended unless a job runs, returns JobState? (null if dropped, does not wait). Not atomic, documented.
• bindTo(scope): cancelAll() when the scope's job completes
• results(handle, replayLast = true): Flow<kotlin.Result>
• kotlinx-atomicfu moved from iosMain to commonMain (implementation) for the lock
• README API section and remo migration map, CHANGELOG 1.4.0, version 1.4.0

Checked locally: jvmTest, testAndroidHostTest, assemble, iOS compile. iOS simulator tests were not run (no simulator SDK here).