docs: use ticdc-version variable in TiCDC examples

[doc-claw-bot]

What is changed, added or deleted? (Required)

• Add ticdc-version to variables.json
• Replace hard-coded TiCDC example versions in ticdc/ticdc-architecture.md with v{{{ .ticdc-version }}}
• Keep the release-threshold statements (v8.5.4 / v8.5.4-release.1) unchanged and update only example snippets and example commands

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

• master (the latest development version)
• v8.5 (TiDB 8.5 versions)
• v8.4 (TiDB 8.4 versions)
• v8.3 (TiDB 8.3 versions)
• v8.2 (TiDB 8.2 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: docs: use ticdc-version variable in TiCDC examples docs#23696
• Other reference link(s): https://github.com/doc-claw-bot/docs/pull/23696

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
  • 部署文档中的 TiCDC 版本示例改为使用可配置的版本变量。
  • TiCDC 配置、离线包下载及集群更新命令将统一引用当前版本设置。
  • 默认 TiCDC 版本更新为 8.5.8。

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: ASSERTIVE

Plan: Team

Run ID: 763fa4e7-e633-46d3-8a0d-d135b7f6fd22

📥 Commits

Reviewing files that changed from the base of the PR and between 70a923c and 5e913ec.

📒 Files selected for processing (2)

• ticdc/ticdc-architecture.md
• variables.json

Included review availability: Your plan provides up to 4 included reviews per hour; 3 remain after this review.

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📝 Walkthrough

Walkthrough

本次变更新增 TiCDC 版本变量，并将 TiCDC 部署文档中的固定版本替换为模板变量。默认 TiCDC 版本设置为 8.5.8。

Changes

TiCDC 版本模板化

Layer / File(s)	Summary
新增 TiCDC 版本变量 variables.json	新增 ticdc-version 字符串变量，默认值为 8.5.8。
更新 TiCDC 部署示例 ticdc/ticdc-architecture.md	TiDB Operator 配置、离线包下载命令和 tiup cluster patch 命令改用 {{{ .ticdc-version }}} 生成 TiCDC 版本。

Estimated code review effort: 1 (Trivial) | ~5 minutes

Merge Risk: ⚪ Minimal · up to 5e913

This localized documentation change is merge-ready after normal checks and review; no actionable merge-blocking risk remains.

Suggested reviewers: qiancai, ti-chi-bot

🚥 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	标题准确概括了主要变更，即在 TiCDC 示例中使用 ticdc-version 变量。标题简洁、明确，并与变更内容一致。
Description check	✅ Passed	描述包含变更内容、适用版本、相关链接、AI agent involvement 以及变更类型检查项。描述明确说明了保留 release-threshold statements 的范围，整体符合模板要求。

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. (2 skipped: 2 unsupported.)

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[qiancai]

/approve

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: qiancai

The full list of commands accepted by this bot can be found here.

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• OWNERS [qiancai]

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[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch master: #21917.
But this PR has conflicts, please resolve them!