The future `Scheduler::claim_next` hands back completed its node only
after `run`'s future returned. A panic while running (the workspace
unwinds) skipped that completion, so the node stayed `Running` and its
resource units stayed held until the process restarted; later nodes
needing the same resource never started.
The run future is now polled under `catch_unwind`. A panic completes
the node as `Outcome::Failed("runner panicked: <msg>")` with nothing
grown, through the same `complete_growing` path as an ordinary failure:
`AFTER_OK` dependents are skipped, pending children cascade, and the
node's units are released.
The node's future is boxed: wrapping it inline pushed the futures
swarm-controller and hive-c0re spawn over clippy's `large_futures`
limit.
Closes#5058