Add deeplink anchors to dropdown directive

[theletterf]

Fixes #1759

• Turns the existing and inherited :name: parameter into an anchor link for the dropdown title.
• Updates the docs with examples.

I avoided adding a visual indicator because it would have polluted the design of the dropdown.

LLM Disclosure: All the commits in this PR were co-authored by Copilot Enterprise using Claude Sonnet 4

[github-actions]

🔍 Preview links for changed docs

• docs/syntax/dropdowns.md
• docs/testing/nested/index.md

[wajihaparvez]

Thank you! 🎉

[theletterf]

@elastic/docs-engineering PTAL, thanks!

[Mpdreamz]

Do we want to always ensure we can deeplink to dropdowns?

E.g infer :name: if none is provided?

[theletterf]

@Mpdreamz Used the slug class to generate names for dropdowns automatically. Had to add some extra logic to handle dropdowns with :open: because they were triggering the URL update (and we don't want that).

[theletterf]

@Mpdreamz Seems like we've hundreds of duplicated dropdown names. I'm in favour of not generating anchors automatically at this point. :) https://github.com/elastic/docs-builder/actions/runs/17273537579/job/49024386232?pr=1765

[Mpdreamz]

I do think its best if this works uniformly across all drop-down, we might need to create a docs-content issue to address the duplicates on a single page which may hurt SEO too.

[theletterf]

@Mpdreamz So unless we turn the errors into Hints, this PR will be blocked until we make all the dropdown titles unique?

[Mpdreamz]

I think we need a plan, just merging it with hints is not sufficient as hints are too easily ignored and will create PR annotations

Since it effects our links.json generation I want to take extra care as well.

[theletterf]

The only other option I'm thinking of is to just allow manual naming / anchoring and not generating anchors automatically. Then in a second phase we could sweep through docs sets as part of SEO improvements and add autogeneration.

[Mpdreamz]

I think its best to identify all places tackle them and then merge this.

The other way around creates no pressure on actually addressing the issue :) We can create a tracking issue in docs-content to look in to all occurrances.

Will do so next week!

[theletterf]

Not sure how to proceed with this one. Couldn't we just remove the automatic generation of anchors?

[theletterf]

@Mpdreamz This now works as intended in that it automatically generates an anchor for each dropdown if one isn't set.

I also added an Hint for duplicated anchors of any type (heading and dropdowns) and the assembled quantity is staggering: more than 4k duplicated anchors, if the method is correct.

Since dropdown anchors do not interfere with the ToC, which is the biggest source of confusion for users, I would suggest that we move the Hint / detection logic to a separate PR and just merge this one.