docs(openhab): sync 5.2.0 default

[mberlofa]

Summary

• Sync openHAB documentation defaults to 5.2.0.
• Add the openHAB image tag control to the playground with the new pinned default.
• Document the upstream 5.2.0 upgrade notes and Java 21 context.

Validation

• make site-sync-check CHART=openhab
• npm run format:check
• npm run lint
• npm run build
• make release-check REPO=site
• make attribution-check REPO=site

Charts PR: helmforgedev/charts#721

Summary by CodeRabbit

• New Features

  • Added a configurable image tag option for the openHAB runtime, with a new default of 5.2.0.

• Documentation

  • Updated the openHAB chart reference to reflect the new default image version.
  • Added upgrade notes for openHAB 5.2.0, including backup guidance and key compatibility reminders.

[coderabbitai]

📝 Walkthrough

Walkthrough

Updates the openHAB playground configuration to add a pinned Image Tag field defaulting to 5.2.0, and updates the openHAB chart documentation's default image tag along with a new Upgrade Notes section covering backup guidance and Java 21 requirement.

Changes

openHAB 5.2.0 Image Tag Update

Layer / File(s)	Summary
Playground config and docs update src/data/playground-configs.ts, src/pages/docs/charts/openhab.mdx	Adds a Runtime "Image Tag" field (key image.tag, default 5.2.0) to playground configs, updates the docs' default image.tag from 5.1.4 to 5.2.0, and adds an "Upgrade Notes" section covering PVC backups, breaking-change review, and the Java 21 requirement.

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

Possibly related issues

• chore(openhab): upstream image update available (5.1.4 → 5.2.0) charts#702: Addresses the same openHAB image tag bump from 5.1.4 to 5.2.0 with corresponding chart/docs updates.

🚥 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.
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 is concise and accurately reflects the main change: syncing the openHAB default to 5.2.0.
Description check	✅ Passed	The description matches the template's required sections and clearly summarizes the change, with only minor gaps like the unfilled related issue.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch docs/openhab-5.2.0

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