Update NavigationPrefixChecker to skip phantom paths during link resolution.

[Mpdreamz]

We need to do this on both branches as otherwise it requires a certain order for phantom branches to not be validated.

Fixes: https://github.com/elastic/elastic-otel-node/actions/runs/15825603447/job/44606696330

The check was failing unrelated to anything elastic-otel-node. Our check relied on elasticsearch://reference being checked before docs-content://reference but in the current iteration of the links.json checks this did not happen because our dictionaries are unordered (as they should be).

[theletterf]

@cotti @Mpdreamz Seems like the problem now cascades down one step:

Error: 'elasticsearch' defines: 'reference/' that 'docs-content://reference/index.md resolving to '/docs/reference/' conflicts with 

	The following errors and warnings were found in the documentation

Error: 'elasticsearch' defines: 'reference/' that 'docs-content://reference/index.md resolving to '/docs/reference/' conflicts with 
NOTE: docs-content

See #1385

[Mpdreamz]

That PR is out of date, needs an update :)