Highlight terms in search result titles

[RisingOrange]

Summary

This PR makes search results easier to scan by highlighting matched query terms in result titles, so title matching is visually consistent with the excerpt highlighting that Pagefind already provides.

It adds a title-highlighting pass in Search.svelte that runs both when the query changes and when Pagefind updates the results DOM. Pagefind highlights terms in result excerpts via {@html} but renders titles as plain text, so this patch post-processes title links to add <mark> tags for the current query.

Notes

• HTML escaping is applied per-segment after splitting matches from surrounding text, so title text stays safe when written back through innerHTML.
• Matching is Unicode-aware, so searches involving titles like Español, Zürich, or São Paulo highlight correctly instead of stopping at ASCII-only word boundaries.
• The title-highlighting regex is still an approximation of Pagefind's own normalization and matching behavior, so edge cases may not exactly mirror excerpt highlighting for every locale or query.
• The title-highlighting pass reruns on query input as well as DOM mutations, which prevents stale highlights when the visible result DOM does not change between searches.
• Partial query matches still highlight the full word (for example, typing anyo highlights anyone), consistent with how Pagefind highlights matches in excerpts.

Screenshots

Query: "lobbying guide"

Before	After

Query: "if anyone"

Before	After

Query: "if anyo" (partial word; highlights full word "anyone")

Before	After

[netlify]

👷 Deploy request for pauseai pending review.

Visit the deploys page to approve it

Name	Link
🔨 Latest commit	146dfeb

[Wituareard]

For reference: The default weight of h1 elements is 7, but it probably doesn't hurt to boost it further.

[Wituareard]

Also, I just found an unreleased PR handling the exact case described in the issue: Pagefind/pagefind#1003

[RisingOrange]

@Wituareard

Also, I just found an unreleased PR handling the exact case described in the issue: Pagefind/pagefind#1003

Right, this seems to be a very good fit for what we want.
I'm watching releases of https://github.com/Pagefind/pagefind to get notified when it gets released.

For now, we could just add the match highlighting in titles? I updated the PR description.

[RisingOrange]

While working on the title highlighting, I noticed that match highlighting needs to be more complicated than I expected in order to support Unicode.
I think it's a nice little improvement, but I'm less sure it's worth the extra code.