Function run_vm_concurrent 

pub fn run_vm_concurrent(input: &str) -> InterpreterResult

Run a concurrent program on the bytecode VM under the deterministic scheduler (T11): compile to opcodes, then drive the main Vm (and any spawned per-task VMs) through run_until_block via a VmTask. This is the VM analog of [run_program_concurrent]; the default routing still sends concurrent programs to the tree-walker, so this is the explicit VM entry used to exercise and (Phase 5c) differentially compare the VM concurrency tier.