fix: (UGP-14675) add fallback ID extraction in slides block for V2 co…

[vik407]

…nverter transition

Adds a fallback path in slides.js decorate() to handle transitional pages where the V2 converter previously emitted
a fragment block with an anchor <a href="/en/slides/{id}"> instead of a slides block with a bare ID.

The root fix is in exl-html-converter (separate PR) — the markdownit plugin now outputs the correct slides block
with a bare ID.

This fallback protects against:
Pages already cached in CDN with the old fragment-style output that get re-decorated after a CDN miss
Any edge environment where the old converter output persists temporarily

Jira ID: UGP-14675

Test URLs:

• Before: https://main--exlm--adobe-experience-league.aem.live

• After: https://UGP-14675--exlm--adobe-experience-league.aem.live

• After: https://UGP-14675--exlm--adobe-experience-league.aem.live/en/browse?martech=off

• After: https://UGP-14675--exlm--adobe-experience-league.aem.live/en/browse/analytics?martech=off

• After: https://UGP-14675--exlm--adobe-experience-league.aem.live/en/docs?martech=off

• After: https://UGP-14675--exlm--adobe-experience-league.aem.live/en/docs/analytics-learn/tutorials/exporting/data-feeds/find-your-data-feed-id=off

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Commits

• 54c5d10 ❌ (latest)
• 201796c ❌

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	Page	Scores	Audits	Google
📱	/
🖥️	/
📱	/en/browse?martech=off
🖥️	/en/browse?martech=off
📱	/en/browse/analytics?martech=off
🖥️	/en/browse/analytics?martech=off
📱	/en/docs?martech=off
🖥️	/en/docs?martech=off
📱	/en/docs/analytics-learn/tutorials/exporting/data-feeds/find-your-data-feed-id=o ff		Lighthouse returned error: NOT_HTML. The page provided is not HTML (served as MIME type text/plain).
🖥️	/en/docs/analytics-learn/tutorials/exporting/data-feeds/find-your-data-feed-id=o ff		Lighthouse returned error: NOT_HTML. The page provided is not HTML (served as MIME type text/plain).