best-practices: clarify scheduler pool underutilization wording

[yahonda]

What is changed, added or deleted? (Required)

Rewords "which makes resource usage insufficient" to "which results in a lower resource utilization rate" for clarity. The original phrasing is ambiguous and can be misread as "there aren't enough resources" (a shortage), when the intended meaning — confirmed against the Chinese source ("资源利用不充分", literally "resource utilization is insufficient") — is that an oversized thread pool leads to a lower utilization rate (wasted capacity), the opposite concern from a resource shortage.

Opened directly against release-8.5 (rather than master) so it can be picked up by the weekly EN-to-JA translation sync from this branch.

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

• 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)?

• Related code change PR links (if applicable):
• This PR is translated from:
• Other reference link(s):

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

• Documentation
  • Clarified the description of resource utilization in the three-node hybrid deployment guidance.

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• best-practices/three-nodes-hybrid-deployment.md

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📝 Walkthrough

Walkthrough

The documentation updates one sentence in the storage.scheduler-worker-pool-size section. It replaces wording about insufficient resource usage with wording about a lower resource utilization rate.

Changes

Hybrid deployment documentation

Layer / File(s)	Summary
Resource utilization wording best-practices/three-nodes-hybrid-deployment.md	The sentence describing the default thread pool value now states that it results in a lower resource utilization rate.

Priority: ⬇️ Low

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

Change: Other

Merge Risk: ⚪ Minimal · up to 2d62e

This documentation-only clarification is mergeable; no concrete implementation risk remains.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely describes the wording clarification for scheduler pool underutilization.
Description check	✅ Passed	The description explains the wording change and its purpose, identifies the affected TiDB version, documents the release-8.5 target, and includes the AI involvement declaration. Optional reference lin…
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 0…
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.

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