Match result clicks by rank map, guard empty permalinks

Result clicks are attributed via the interceptor's permalink→rank map
rather than a guessed results container, so themes that render links
outside #primary/main still report. Skips permalinks that come back
empty/non-string when building the map.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: jeffreyvr

src/Search/ClickTracking.php

@@ -11,6 +11,10 @@
  * results; events go straight to the Datalumo API through the SDK,
  * tagged with the search session the interceptor's API call returned so
  * each click ties back to the query that produced it.
+ *
+ * Result clicks are matched against the interceptor's permalink→rank map
+ * (not a guessed results container), so theme markup that puts links
+ * outside #primary / main still reports.
  */
 class ClickTracking
 {

src/Search/Interceptor.php

@@ -77,11 +77,17 @@ public function intercept(?array $posts, WP_Query $query): ?array
         $pool = $this->reorder($pool, $query);
 
         // Zero-based, matching the widget SDK's wire convention — the
-        // dashboard renders ranks as #rank+1.
+        // dashboard renders ranks as #rank+1. Keys are the absolute
+        // permalinks themes render; the browser-side matcher normalises
+        // trailing slashes / encoding before comparing.
         $ranks = [];
 
         foreach ($pool as $index => $post) {
-            $ranks[get_permalink($post)] = $index;
+            $permalink = get_permalink($post);
+
+            if (is_string($permalink) && $permalink !== '') {
+                $ranks[$permalink] = $index;
+            }
         }
 
         self::$lastSearch = [