Clarify TiKV large-row limit in transaction restraints

[doc-claw-bot]

What is changed, added or deleted? (Required)

Clarify in develop/dev-guide-transaction-restraints.md that increasing the large-row limit in TiDB is not sufficient by itself. When a single write request exceeds TiKV raftstore.raft-entry-max-size, TiKV rejects the request, so users need to adjust the TiKV limit together with the TiDB row-size limit.

Which TiDB version(s) do your changes apply to? (Required)

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By default, CHOOSE MASTER ONLY so your changes will be applied to the next TiDB major or minor releases. If your PR involves a product feature behavior change or a compatibility change, CHOOSE THE AFFECTED RELEASE BRANCH(ES) AND MASTER.

For details, see tips for choosing the affected versions (in Chinese).

• master (the latest development version)
• v9.0 (TiDB 9.0 versions)
• v8.5 (TiDB 8.5 versions)
• v8.1 (TiDB 8.1 versions)
• v7.5 (TiDB 7.5 versions)
• v7.1 (TiDB 7.1 versions)
• v6.5 (TiDB 6.5 versions)

What is the related PR or file link(s)?

• This PR is translated from:
• Other reference link(s): https://docs.pingcap.com/zh/developer/dev-guide-transaction-restraints/#大事务限制

AI agent involvement

• The changes in this PR were primarily made by an AI agent on behalf of the PR author.

Do your changes match any of the following descriptions?

• Delete files
• Change aliases
• Need modification after applied to another branch
• Might cause conflicts after applied to another branch

Summary by CodeRabbit

• 文档
  • 补充“大事务限制”说明：TiKV 也会限制“单次写入请求”的数据量大小。
  • 当单次写入超过默认 raftstore.raft-entry-max-size（8 MiB）时，TiKV 将拒绝处理该请求。
  • 在“大行记录”场景下，建议联动调整 TiDB tidb_txn_entry_size_limit 与 TiKV raftstore.raft-entry-max-size。

[coderabbitai]

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📝 Walkthrough

Walkthrough

在“大事务限制”章节补充 TiKV 写入请求大小限制，说明 raftstore.raft-entry-max-size 默认值为 8 MiB，以及大行记录场景下需同时调整 TiDB 和 TiKV 侧限制。

Changes

事务限制文档

Layer / File(s)	Summary
补充 TiKV 写入请求限制说明 develop/dev-guide-transaction-restraints.md	说明超过 raftstore.raft-entry-max-size 默认 8 MiB 的写入请求会被 TiKV 拒绝，并补充大行记录下的配置调整说明。

Estimated code review effort: 1 (Trivial) | ~2 minutes

Suggested labels: needs-cherry-pick-release-7.5

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	标题准确概括了本次对 TiKV 大行限制说明的澄清。
Description check	✅ Passed	描述包含变更内容、适用版本、相关链接和 AI 参与信息，整体符合模板要求。
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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Actionable comments posted: 1

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ℹ️ Review info

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📥 Commits

Reviewing files that changed from the base of the PR and between d29bc18 and 7838533.

📒 Files selected for processing (1)

• develop/dev-guide-transaction-restraints.md

[qiancai]

/approve

[qiancai]

/approve

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[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: qiancai

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[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-8.1: #21833.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-8.5: #21834.