Effect Circuit Breaker and Retry Budget

Resilience primitives that stop a wobbling dependency from becoming a self-inflicted outage. The retry budget is an atomic token bucket over a Ref: traffic funds tokens, each retry spends one, and an empty bucket rewrites the failure into a non-retryable error, so retries can never exceed a fixed percentage of live traffic no matter how many callers are failing at once. Backoff is Schedule.jittered over Schedule.exponential so a synchronized retry wave desynchronizes. The circuit breaker is a Ref state machine (closed, open, half-open) keyed on the Clock that admits exactly one half-open probe before deciding to close or re-open, and a per-dependency Semaphore bulkhead fails fast so one slow dependency cannot exhaust the shared fiber pool. Every call carries an Effect.timeout. Solves retry storms and cascading failures. Pinned to effect 4.0.0-beta.98.