docs: remove stray zero-width-space characters from prose

[yahonda]

What is changed, added or deleted? (Required)

Removes stray zero-width-space (U+200B) characters embedded in prose across 13 files (37 occurrences total), found while investigating the same artifact in the i18n-ja-release-8.5 translation branch (see #23792).

These characters are invisible in rendered output but present in the raw Markdown source, most commonly appearing as a doubled zero-width space between two words (e.g. "values​​of" reads visually as "values of" but has 2 hidden characters between them).

Scoped narrowly to files where the corresponding docs-cn content does not have the same characters (confirmed via the docs-cn GitHub API), to avoid touching content that might have a shared/intentional origin. 3 other files found with this same artifact (dm/dm-binlog-event-filter.md, dm/dm-block-allow-table-lists.md, releases/release-6.0.0-dmr.md) were deliberately excluded from this PR since docs-cn has the identical characters there too — left for separate investigation.

See #23792 for the original report and open question to maintainers about whether this is intentional.

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): Zero-width space (U+200B) characters found embedded in release-8.5 English content #23792, i18n(ja): remove stray zero-width-space MT artifacts #23778

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
  • Corrected invisible and variant whitespace characters across configuration, SQL, diagnostics, encryption, information schema, statistics, and literal-value documentation.
  • Cleaned formatting in historical release notes without changing their content or issue references.
  • Improved consistency and readability of documentation text and examples.

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No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: ASSERTIVE

Plan: Advanced

Run ID: 34d4c6b1-9e0c-493e-908b-8eb198126acf

📥 Commits

Reviewing files that changed from the base of the PR and between 1b0fd93 and 8f91e70.

📒 Files selected for processing (13)

• constraints.md
• dashboard/dashboard-diagnostics-report.md
• develop/dev-guide-join-tables.md
• encryption-at-rest.md
• information-schema/information-schema-data-lock-waits.md
• information-schema/information-schema-deadlocks.md
• information-schema/information-schema-tidb-trx.md
• literal-values.md
• releases/release-5.1.5.md
• releases/release-5.3.2.md
• releases/release-5.4.3.md
• releases/release-6.1.0.md
• statistics.md

Included review availability: Your plan provides up to 4 included reviews per hour; 0 remain after this review.

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📝 Walkthrough

Walkthrough

This documentation-only change removes invisible or variant whitespace characters from technical documentation and release notes. Visible wording, documented behavior, issue links, and functional code remain unchanged.

Changes

Documentation normalization

Layer / File(s)	Summary
Normalize documentation text constraints.md, dashboard/*, develop/dev-guide-join-tables.md, encryption-at-rest.md, information-schema/*, literal-values.md, releases/*, statistics.md	Removes invisible whitespace characters from documentation descriptions, examples, field references, join guidance, histogram text, and release-note entries without changing their visible content.

Priority: ⬇️ Low

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

Merge Risk: ⚪ Minimal · up to 8f91e

This change normalizes invisible whitespace in documentation and release notes without changing visible content or product behavior. No current merge-readiness risk remains.

Suggested reviewers: qiancai

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely describes the main change: removing stray zero-width-space characters from documentation prose.
Description check	✅ Passed	The description covers the required change summary, affected versions, related issues, AI involvement, and change classifications. It provides scope, rationale, exclusions, and file-count details.
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.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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