Cover every placement variant + failure mode of the new
`to_actor.run()`,
- private-nursery one-shot + implicit runtime boot via pass-through
`runtime_kwargs`,
- remote-error relay to the caller's task (bare and inside a
caller-managed `an`) as boxed `RemoteActorError`s,
- caller-nursery spawn + portal-reuse w/o implicit reap,
- the concurrent "worker-pool-ish" pattern: a local `trio` task
nursery scheduling one-shots against a shared `an`,
- the 4 pre-spawn validation rejections (sync fn, async-gen fn,
`portal`+`an` combo, `runtime_kwargs`+placement combo).
(this patch was generated in some part by [`claude-code`][claude-code-gh])
[claude-code-gh]: https://github.com/anthropics/claude-code
Gud Boi