RunQueueSettings

The run queue's own settings (design 4.55), loaded from llm4s.agent.queue by RunQueueConfigLoader:

• maxAttempts: the most attempts an entry makes before it is closed Failed(AttemptsExhausted) (default RunQueueSettings.DefaultMaxAttempts). Fixed on each entry at submission, so every worker agrees on it.
• ticketLifetime: how long a closed entry - its input, attempts and outcome - is kept after it closed, by the store's clock, before the retention sweep reclaims it (default RunQueueSettings.DefaultTicketLifetime). Waiting on or following a reclaimed ticket answers QueueError.TicketExpired.
• lease: the LeasePolicy a worker leases entries with.

maxAttempts must be at least 1 and ticketLifetime positive: apply and the with* setters throw IllegalArgumentException otherwise, and RunQueueSettings.of returns a ValidationError.