[BUG] — Disruptor consumer→executor handoff to an unbounded `LinkedBlockingQueue` breaks backpressure

- severity: High
- files: `shenyu-disruptor/src/main/java/org/apache/shenyu/disruptor/DisruptorProviderManage.java:108-110` (`OrderlyExecutor(consumerSize, consumerSize, 0, MS, new LinkedBlockingQueue<>(), ..., AbortPolicy)`), `shenyu-disruptor/src/main/java/org/apache/shenyu/disruptor/thread/SingletonExecutor.java:32-34` (1,1,0,`new LinkedBlockingQueue<>()`), `QueueConsumer.java:58` (`executor.execute(queueConsumerExecutor)`)
- description: The Disruptor ring buffer (`DEFAULT_SIZE=16384`) is bounded, but `QueueConsumer.onEvent` hands each consumed event to an executor backed by an *unbounded* queue. When consumers are slower than producers (e.g. admin persisting registrations to DB), the executor queue grows without bound → OOM. `AbortPolicy` is dead code (an unbounded queue never rejects). For orderly events the single `SingletonExecutor` thread is the per-key bottleneck.
- impact: `RegisterClientServerDisruptorPublisher` (admin) and `ShenyuClientRegisterEventPublisher` (client) accumulate unbounded queued tasks under registration burst / DB slowdown.
- suggested_fix: Bound the executor queue (`ArrayBlockingQueue` sized to ring-buffer slots) with `CallerRunsPolicy` (or block-the-producer) so Disruptor backpressure propagates to the consumer.
- confidence: High

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_Identified during the 2026-08-02 deep re-scan; full list in [`docs/scan2-2026-08-02/00-consolidated-critical-high.md`](docs/scan2-2026-08-02/00-consolidated-critical-high.md)._

Start with QueueConsumer.onEvent and trace the executor construction at DisruptorProviderManage.java:108-110 and thread/SingletonExecutor.java:32-34. Compare the handoff used by RegisterClientServerDisruptorPublisher and ShenyuClientRegisterEventPublisher; done means their executor queues are bounded or block the producer so registration bursts cannot grow queued tasks without limit.

Written by the indexing model from the issue text.