[Bug]: lower_case_table_names.sql row 129 flaky — lower_case_table_names value mismatch in multi-CN PROXY

## Problem

`lower_case_table_names.sql` row 129 fails in multi-CN PROXY BVT:

```sql
select @@lower_case_table_names;
Expected: 1
Actual: 0
```

The test sets `lower_case_table_names=1` but a different CN in the PROXY cluster returns `0`. This is a multi-CN system variable propagation timing issue — the variable change hasn't propagated to all CNs when the query executes on a different CN.

## Recent Occurrences

| Date | PR/Run | Job |
|---|---|---|
| 2026-08-18 | [PR #27227](https://github.com/matrixorigin/matrixone/actions/runs/32104863887/job/95613494743) | BVT PROXY |

## Suggested Fix

1. Add `SET GLOBAL lower_case_table_names = 1` with explicit wait/sync before querying
2. Or use `-- @retry` or `-- @ignore` directives for multi-CN variable propagation timing
3. Or increase variable propagation timeout in PROXY environment