⚡ Bolt: Optimize circuit breaker fast path to prevent DashMap write lock contention

[ovasylenko]

💡 What: Introduced a fast-path read lock using self.breakers.get(q) at the beginning of record_failure in the circuit breaker registry. If the breaker is already fully Open, it returns early instead of acquiring a write lock to increment the failure_count.
🎯 Why: During a failure storm, many in-flight requests may fail sequentially or concurrently. The previous implementation acquired a get_mut() write lock on the DashMap shard for every failure to increment the failure_count. However, once a circuit is Open, the failure_count has no behavioral impact on cooldown timers or recovery. Avoiding the write lock entirely removes severe contention on the specific DashMap shard.
📊 Impact: Completely eliminates write-lock contention on the hot path for failing services once their circuit is open, dramatically reducing CPU overhead during cascading failures.
🔬 Measurement: Verify via cargo check, cargo fmt, cargo clippy, and cargo test -p orch8-engine --lib circuit_breaker.

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PR created automatically by Jules for task 12300898650048027779 started by @ovasylenko

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