Search: a word with a leading ^ matches at a word's start only

"^zed" finds "Zed Dead", "The_Zed_Files", not "Facialized": a regex on
release_texts, (^|[^[:alnum:]]) before the word, which the trigram index
serves (homelab: 551 texts for ^zed against 6,606 for zed, 35 ms warm).
Words without ^ match anywhere as before; the search box says so.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

public/index.html

@@ -22,7 +22,7 @@
           <label class="search-box">
             <svg aria-hidden="true" viewBox="0 0 24 24"><circle cx="11" cy="11" r="7" /><path d="m20 20-3.5-3.5" /></svg>
             <input id="q" type="search" autocomplete="off" spellcheck="false"
-                   placeholder="Search release names…" aria-label="Search" />
+                   placeholder="Search release names… (^word: at a word's start)" aria-label="Search" />
             <kbd aria-hidden="true">/</kbd>
           </label>
           <label class="select">