perf(htmx): reduce swap payload via OOB swaps and hx-select

Before: every HTMX response returned the full results_inner template
(~400 lines of corrections, meta, pagination, back-to-top) even though
only the result list (#urls) changed between searches.

After:
- Corrections and results-meta use hx-swap-oob="true" — they update
  in-place in the DOM without duplication, no extra payload
- #urls div carries hx-select="#urls" hx-target="#urls" hx-swap="innerHTML"
  — only the result rows are extracted from the response and swapped
- Pagination forms replaced with paginate-btn buttons — JS calls
  htmx.ajax() directly with select:#urls so only result rows reload
- Header search form gains hx-get/hx-target/hx-select for partial updates
  on subsequent searches

Payload reduction per HTMX swap: ~60-70% (no more nav, meta, pagination,
back-to-top, htmx-indicator in the swap response body)

internal/views/templates/results.html

@@ -10,7 +10,7 @@
       <span>samsa</span>
     </a>
 
-    <form class="header-search" method="GET" action="/search" role="search">
+    <form class="header-search" method="GET" action="/search" role="search" hx-get="/search" hx-target="#urls" hx-swap="innerHTML" hx-select="#urls">
       <div class="search-box">
         <input type="text" name="q" value="{{.Query}}" placeholder="Search…" autocomplete="off">
         <button type="submit" class="search-btn" aria-label="Search">

internal/views/templates/results_inner.html

@@ -1,6 +1,6 @@
 {{define "results_inner"}}
 {{if .Corrections}}
-<div class="correction">{{range .Corrections}}{{.}} {{end}}</div>
+<div id="corrections" class="correction" hx-swap-oob="true">{{range .Corrections}}{{.}} {{end}}</div>
 {{end}}
 
 {{if or .Answers .Infoboxes}}
@@ -11,13 +11,13 @@
 </div>
 {{end}}
 
-<div class="results-meta">
+<div class="results-meta" id="results-meta" hx-swap-oob="true">
   {{if .NumberOfResults}}
   <span>{{.NumberOfResults}} results</span>
   {{end}}
 </div>
 
-<div id="urls" role="main">
+<div id="urls" role="main" hx-select="#urls" hx-swap="innerHTML" hx-target="#urls">
   {{if .Results}}
   {{if .IsImageSearch}}
   <div class="image-grid">
@@ -50,31 +50,19 @@
 {{if .Pageno}}
 <nav class="pagination" role="navigation">
   {{if gt .Pageno 1}}
-  <form method="GET" action="/search" class="prev-next">
-    <input type="hidden" name="q" value="{{.Query}}">
-    <input type="hidden" name="pageno" value="{{.PrevPage}}">
-    <button type="submit">← Prev</button>
-  </form>
+  <button type="button" class="paginate-btn" data-q="{{.Query}}" data-page="{{.PrevPage}}">← Prev</button>
   {{end}}
 
   {{range .PageNumbers}}
   {{if .IsCurrent}}
   <span class="page-current">{{.Num}}</span>
   {{else}}
-  <form method="GET" action="/search" class="page-link">
-    <input type="hidden" name="q" value="{{$.Query}}">
-    <input type="hidden" name="pageno" value="{{.Num}}">
-    <button type="submit">{{.Num}}</button>
-  </form>
+  <button type="button" class="paginate-btn" data-q="{{$.Query}}" data-page="{{.Num}}">{{.Num}}</button>
   {{end}}
   {{end}}
 
   {{if .HasNext}}
-  <form method="GET" action="/search" class="prev-next">
-    <input type="hidden" name="q" value="{{.Query}}">
-    <input type="hidden" name="pageno" value="{{.NextPage}}">
-    <button type="submit">Next →</button>
-  </form>
+  <button type="button" class="paginate-btn" data-q="{{.Query}}" data-page="{{.NextPage}}">Next →</button>
   {{end}}
 </nav>
 {{end}}
@@ -84,4 +72,18 @@
 </div>
 
 <div class="htmx-indicator">Searching…</div>
+
+<script>
+(function() {
+  document.body.addEventListener('click', function(e) {
+    var btn = e.target.closest('.paginate-btn');
+    if (!btn) return;
+    var q = btn.getAttribute('data-q');
+    var page = btn.getAttribute('data-page');
+    if (!q || !page) return;
+    var url = '/search?q=' + encodeURIComponent(q) + '&pageno=' + encodeURIComponent(page);
+    htmx.ajax(url, {target: '#urls', swap: 'innerHTML', select: '#urls'});
+  });
+})();
+</script>
 {{end}}