[BUG] Multi-client consume forEach breaks on single selector failure

- severity: Medium
- files: `shenyu-plugin/shenyu-plugin-logging/shenyu-plugin-logging-common/.../AbstractLogCollector.java:120-128`
- description: In the multi-client path, `bufferQueueS.forEach((selectorId, bufferQueue) -> { ... processBufferQueue(...); })` wraps any exception in `throw new RuntimeException(e)`, breaking the `forEach` iteration. If one selector's log processing throws, all remaining selectors are skipped for that cycle.
- impact: A transient failure in one selector's backend blocks log delivery for all other selectors for at least one consume cycle.
- suggested_fix: Wrap each selector's processing in an individual try-catch inside the forEach lambda.
- confidence: Medium
- related_existing: none

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_Identified during the 2026-08-02 deep re-scan; full list in [`docs/scan2-2026-08-02/06-medium-tiers.md`](docs/scan2-2026-08-02/06-medium-tiers.md)._

Start in shenyu-plugin/shenyu-plugin-logging/shenyu-plugin-logging-common/.../AbstractLogCollector.java:120-128 and inspect the multi-client bufferQueueS.forEach lambda. Verify that an exception while processing one selector is isolated so later selectors still run in the same consume cycle. Done means a single selector failure no longer stops log delivery for the remaining selectors.

Written by the indexing model from the issue text.