Exposes Kotlin's Channel<Obj> to Lyng scripts as a first-class type with rendezvous, buffered, and unlimited capacity modes. Supports suspending send/receive, non-suspending tryReceive, close/drain semantics, and isClosedForSend/isClosedForReceive properties. Also fixes a pre-existing typo in BookTest.kt that blocked JVM test compilation, and adds Channel reference docs and a parallelism.md section. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>