InboxRegistry::register returned (Uuid, Receiver) even when the inner
Mutex was poisoned — `if let Ok(mut g) = self.inner.lock()` swallowed
the error, the sender was never inserted, the later deliver(id, …)
saw no entry and returned Abandoned, and the caller's `await rx`
blocked until the orchestrator's outer timeout.
Sister registries (RouteTable, AppDomainTable) already .expect()
panic on poison. Make InboxRegistry::{register, cancel, deliver} loud
in the same way.
A poisoned Mutex means a prior panic inside a critical section — the
process is unrecoverable; silently swallowing it just defers the
crash and corrupts the inbox protocol on the way.
AUDIT.md anchors: F-Q-006 (register), F-Q-010 (consistency policy).
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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