Added at merge review. none() held a clock frozen at 0 with a 1ns cooldown, so
a quarantine() call on it recorded a deadline that could never pass — the
credential would be locked out for the life of the daemon. Two production
CompositePeerLauncher constructors default to none(), so that failure would
have been silent and permanent.
The implementer documented the limitation honestly rather than hiding it, but
a stand-in named none() should not need the caveat. quarantine() is now a
no-op on that instance, with a test asserting it. An inert value must omit the
fact, never invent one.
A BACKEND_EXHAUSTED classification (stage A) now puts that profile's
credential into a BackendQuarantine for a configurable cooldown. A spawn
onto a quarantined profile is refused naming the credential and roughly
when it lifts; weighted/round-robin/fixed placement skip a quarantined
candidate; the quarantine lifts itself on the injected clock; and it is
visible on bridge_profiles.
Keyed by credential, not by profile name, via the new Profile.credentialId
(profiles sharing one credential quarantine together — e.g. two models on
one account) and effectiveCredentialId() (unset ⇒ quarantines alone,
today's behaviour unchanged). Fixed a related gap along the way: a reload
changing exhaustedPattern was silently reported "applied" even though it's
deferred — sameLaunchSettings() now catches it too.
Dai Ha