Race `IPCServer.wait_for_peer(uid)` against the sub-proc's
`.wait()` inside a `trio` nursery; whichever completes first
cancels the other.
Prevents the spawning task from parking forever on an unsignalled
`_peer_connected[uid]` event when a sub-actor dies during boot
(e.g. crashed on import before reaching `_actor_child_main`).
Instead of hanging, raises `ActorFailure` w/ the proc's exit code
for clean supervisor error reporting.
Also,
- use the new racer in `main_thread_forkserver_proc()` spawn path.
- keep `proc_wait` generic so each backend passes its own callable
(`trio.Process.wait`, `_ForkedProc.wait`, etc.).
(this patch was generated in some part by [`claude-code`][claude-code-gh])
[claude-code-gh]: https://github.com/anthropics/claude-code
(cherry picked from commit 3b0724eba8)
Gud Boi
7256570954