docs(castopod): sync template standards

[mberlofa]

Summary

• register castopod in the site sync playground registry
• keep the playground/site sync gate aligned with the chart validation PR

Validation

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

Chart PR: helmforgedev/charts#649
Issue: helmforgedev/charts#633

Summary by CodeRabbit

• New Features
  • Added support for the castopod chart in the playground, making it eligible to appear in chart selection and maturity filtering.

[coderabbitai]

📝 Walkthrough

Walkthrough

This PR adds castopod to siteSyncPlaygroundConfigs in the playground page, changing which chart slug is included in the configured set and eligible for playground chart filtering.

Changes

Playground Config Update

Layer / File(s)	Summary
Add castopod to site sync configs src/pages/playground.astro	Adds castopod to siteSyncPlaygroundConfigs, affecting configuredChartSlugs computation and playgroundCharts filtering.

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

Possibly related PRs

• helmforgedev/site#322: Also adds a chart slug to siteSyncPlaygroundConfigs in src/pages/playground.astro, affecting the same playground filtering path.
• helmforgedev/site#330: Modifies the same playground config map to register another chart slug, with similar eligibility logic changes.

Related issues: None specified

Suggested labels: none

Suggested reviewers: None specified

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 inconclusive)

Check name	Status	Explanation	Resolution
Title check	❓ Inconclusive	The title is related to the castopod sync change, but it is vague and doesn’t clearly state the main code-level update.	Use a specific title that names the castopod registry/gate change, such as adding Castopod to the site sync playground registry.

✅ Passed checks (4 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.
Description check	✅ Passed	The description covers the summary, validation commands, and linked issue; only the template’s checklist-style Quality Gates section is loosely formatted.

✨ 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/castopod-template-standards-sync

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