i18n(ja): fix scrambled sentence and mistranslated Key Visualizer link

[yahonda]

What is changed, added or deleted? (Required)

Found while reviewing PR #23626: performance-tuning-overview.md's paragraph describing performance-measurement dimensions had its links scrambled across two EN sentences. EN structure:

1. "TiDB measures and stores performance data thoroughly in different dimensions, such as [slow query logs], [Top SQL], [Continuous Performance Profiling], and [traffic visualizer]."
2. "In addition, you can perform historical backtracking and comparison of the timing metrics data stored in Prometheus." (no links)

The JA translation only kept 2 of the 4 dimension links in the first sentence, and stuffed the other 2 (Top SQL, and a mistranslated "Key Visualizer" link rendered as 交通ビジュアライザー) into the second (link-free) sentence, making it ungrammatical.

Reconstructed to match EN's actual two-sentence structure with all 4 links in the first sentence, and fixed the Key Visualizer link text — it was rendered as 交通ビジュアライザー, a literal translation of "traffic visualizer", the generic phrase this one EN sentence used instead of the established "Key Visualizer" proper noun that's kept in English everywhere else in the corpus (a separate EN-side fix for that inconsistency is being filed against master).

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

• i18n-ja-release-8.5 (TiDB Japanese documentation for TiDB 8.5 versions)

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

• This PR is translated from:
• Other reference link(s): found while reviewing i18n(ja): fix dropped topic-marker particle before predicates #23626

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
  • Updated performance baseline guidance to identify supported TiDB performance data sources.
  • Clarified coverage for slow query logs, Top SQL, continuous profiling, Key Visualizer, and historical Prometheus metrics.

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No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

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• performance-tuning-overview.md

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📝 Walkthrough

Walkthrough

パフォーマンスチューニング概要で、パフォーマンスデータの参照先とPrometheus履歴メトリクスとの比較方法を明示した。

Changes

パフォーマンスデータ参照先

Layer / File(s)	Summary
データ参照先の記述更新 performance-tuning-overview.md	スロークエリログ、Top SQL、継続的なパフォーマンスプロファイリング、Key Visualizer、Prometheus履歴メトリクスの参照方法を整理した。

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

Merge Risk: ⚪ Minimal · up to f10d1

This is a localized Japanese documentation correction with no actionable merge-blocking risk remaining beyond normal checks and review.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
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.
Title check	✅ Passed	The title clearly describes the main changes: fixing the Japanese translation and correcting the Key Visualizer link text.
Description check	✅ Passed	The description covers the required change summary, affected TiDB version, related reference, AI involvement, and change-type checklist. The blank translated-from field is non-critical.

Full details: Docstring Coverage

Explanation

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 files. (1 skipped: 1 unsupported.)

✨ Finishing Touches 💡 1

🛠️ Fix failing CI checks 💡

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix-performance-tuning-overview-scramble

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Actionable comments posted: 1

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• performance-tuning-overview.md

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2026-08-28 08:17:40.499186206 +0000 UTC m=+835295.670280334: ☑️ agreed by qiancai.