performance-tuning-overview: use Key Visualizer proper noun consistently

[yahonda]

What is changed, added or deleted? (Required)

Found while reviewing a Japanese translation fix (docs#23627): performance-tuning-overview.md linked to the Key Visualizer feature page (/dashboard/dashboard-key-visualizer.md) using the generic link text "traffic visualizer" instead of the established proper noun "Key Visualizer" used consistently everywhere else this feature is referenced (TOC.md, troubleshoot-hot-spot-issues.md, tidb-cloud/tune-performance.md, develop/dev-guide-use-follower-read.md, etc.).

This inconsistency also caused the Japanese translation to render it as a literal (and confusing) "交通ビジュアライザー" ("traffic" in the transportation sense) instead of keeping the established English term.

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

• master

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

• Related: i18n(ja): fix scrambled sentence and mistranslated Key Visualizer link #23627 (the Japanese translation fix this was found while reviewing)

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 the performance baseline documentation link text to clearly reference the Key Visualizer dashboard.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

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📥 Commits

Reviewing files that changed from the base of the PR and between ff98075 and 05db1b8.

📒 Files selected for processing (1)

• performance-tuning-overview.md

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📝 Walkthrough

Walkthrough

The performance baseline documentation updates the Key Visualizer dashboard link text from “traffic visualizer” to “Key Visualizer”.

Changes

Key Visualizer documentation

Layer / File(s)	Summary
Update dashboard link label performance-tuning-overview.md	The performance baseline section uses “Key Visualizer” as the dashboard link text.

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

Merge Risk: ⚪ Minimal · up to 05db1

This localized documentation-only change standardizes the Key Visualizer name without affecting runtime behavior; no actionable merge-blocking risk remains after normal checks and review.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly identifies the documentation file and the primary change: consistent use of the “Key Visualizer” proper noun.
Description check	✅ Passed	The description explains the change and its reason, identifies the applicable master version, provides a related PR, and completes the AI involvement and change-type sections.
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.

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

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix-en-key-visualizer-term

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2026-09-03 04:17:06.827710952 +0000 UTC m=+1339261.998805054: ☑️ agreed by qiancai.

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@qiancai: Your lgtm message is repeated, so it is ignored.

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[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: base branch (master) needs to differ from target branch (master).