[BUG] Swallowed exceptions in close methods across logging clients

- severity: Medium
- files: `shenyu-plugin/shenyu-plugin-logging/shenyu-plugin-logging-common/.../AbstractLogConsumeClient.java:91`; `.../shenyu-plugin-logging-huawei-lts/.../HuaweiLtsLogCollectClient.java:123`; `.../shenyu-plugin-logging-tencent-cls/.../TencentClsLogCollectClient.java:118`
- description: In `close()`/`close0()`, the catch block logs `LOG.error("... close error.")` but does NOT pass the exception `e` as an argument, so the stack trace is permanently lost.
- impact: Resource close failures are silently swallowed with no stack trace, making debugging impossible.
- suggested_fix: Pass the exception: `LOG.error("... close error.", e)`.
- confidence: High
- 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 by reading the close()/close0() catch blocks at AbstractLogConsumeClient.java:91, HuaweiLtsLogCollectClient.java:123, and TencentClsLogCollectClient.java:118. Confirm each close-error log includes the caught exception, then verify that all three logging clients preserve the exception stack trace when closing fails.

Written by the indexing model from the issue text.