[fiesta] Warn on duplicate fragment references within a page

[shkhan91]

• When the same fragment path is referenced more than once on a single page, authors receive no feedback
• This silent duplication is typically a copy-paste error
• The fix must emit exactly one console warning per duplicated path without altering load/render behaviour

Resolves:

Test URLs:

• Before: https://stage--milo--adobecom.aem.page/?martech=off
• After: https://duplicate-fragment-references-5563df--milo--shkhan91.aem.page/?martech=off

[aem-code-sync]

Hello, I'm the AEM Code Sync Bot and I will run some actions to deploy your branch and validate page speed.
In case there are problems, just click a checkbox below to rerun the respective action.

• Re-run all PSI checks
• Re-run failed PSI checks
• Re-sync branch

Commits

• 3840fa8 ❌ (latest)

[aem-code-sync]

	Page	Scores	Audits	Google
📱	/?martech=off		Lighthouse returned error: NOT_HTML. The page provided is not HTML (served as MIME type text/plain).
🖥️	/?martech=off		Lighthouse returned error: NOT_HTML. The page provided is not HTML (served as MIME type text/plain).