fix(clickhouse): register table comments via command instead of inline CTAS

[cookieark7]

Description

Fixes #5969.

ClickhouseEngineAdapter sets COMMENT_CREATION_VIEW but never COMMENT_CREATION_TABLE, so it falls back to the base default IN_SCHEMA_DEF_CTAS and embeds COMMENT '...' in CREATE TABLE ... AS SELECT, which Cloud rejects:

Code: 62. DB::Exception: Syntax error: failed at position 198 (COMMENT):
COMMENT 'test table description' AS SELECT ... Expected one of: AS, end of query.

Setting it to COMMENT_COMMAND_ONLY keeps the comment out of the CTAS and routes the table and column descriptions through the existing ALTER TABLE ... MODIFY COMMENT / ... COMMENT COLUMN paths, same as views already do.

Test Plan

Heads up: these tests only fail on Cloud. They pass against the Docker ClickHouse behind make clickhouse-test both before and after this change (I checked 24.7 and 26.8.1 — both accept the inline COMMENT), so I couldn't reproduce the Cloud failure locally.

What I could verify is that the CTAS no longer carries a COMMENT at all:

-- before
CREATE TABLE "t" ENGINE=MergeTree ORDER BY () AS (SELECT ...) COMMENT 'test table description'

-- after
CREATE TABLE "t" ENGINE=MergeTree ORDER BY () AS SELECT ...
ALTER TABLE "t" MODIFY COMMENT 'test table description'
ALTER TABLE "t" COMMENT COLUMN "id" 'test id column description'

Since the inline COMMENT is gone entirely, its position no longer matters. Leaving the actual Cloud confirmation to the clickhouse-cloud-test job here.

Locally: make clickhouse-test 168 passed, make fast-test 2621 passed, make style clean.

Checklist

• I have run make style and fixed any issues
• I have added tests for my changes (if applicable) — none added; the two existing tests in CI Fix - Clickhouse-Cloud CI Currently Failing #5969 cover it
• All existing tests pass (make fast-test)
• My commits are signed off (git commit -s) per the DCO

[mday-io]

Good find. Thanks - approving and merging.

[cookieark7]

Welcome !