Fix Mastodon/Bsky duplicate replies in webmentions.js

webmentions.js was adding NEW cards for Mastodon replies even when
Alpine had already rendered them, because the client-side filter didn't
mirror the Nunjucks build-time fed.brid.gy exclusion rule.

Pass mastodon-active + bsky-url as data attributes on the webmentions
container div, then filter out fed.brid.gy sourced Mastodon replies
and bsky.app/brid.gy/bluesky Bluesky replies from regularItems when
the corresponding Alpine component is active.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

_includes/components/webmentions.njk

@@ -12,6 +12,8 @@
      data-target="{{ absoluteUrl }}"
      data-domain="{{ site.webmentions.domain }}"
      data-buildtime="{{ buildTimestamp }}"
+     data-mastodon-active="{{ 'true' if mastodonInstance else '' }}"
+     data-bsky-url="{{ bskySyndUrl }}"
      class="hidden"></div>
 
 {# Detect Bluesky syndication URL here — needed to show section even without webmentions #}

js/webmentions.js

@@ -10,6 +10,8 @@
   const target = container.dataset.target;
   const domain = container.dataset.domain;
   const buildTime = parseInt(container.dataset.buildtime, 10) || 0;
+  const mastodonActive = container.dataset.mastodonActive === 'true';
+  const bskyUrl = container.dataset.bskyUrl || '';
 
   if (!target || !domain) return;
 
@@ -66,7 +68,15 @@
 
     // Separate owner replies (threaded under parent) from regular interactions
     var ownerReplies = allChildren.filter(function(wm) { return wm.is_owner && wm.parent_url; });
-    var regularItems = allChildren.filter(function(wm) { return !wm.is_owner && !isSelfBsky(wm); });
+    var regularItems = allChildren.filter(function(wm) {
+      if (wm.is_owner || isSelfBsky(wm)) return false;
+      var src = (wm['wm-source'] || '').toLowerCase();
+      var authorUrl = ((wm.author && wm.author.url) || '').toLowerCase();
+      // Mirror Nunjucks build-time filters: skip platform replies handled by Alpine
+      if (mastodonActive && src.includes('fed.brid.gy')) return false;
+      if (bskyUrl && (src.includes('bsky.app') || src.includes('brid.gy/bluesky') || authorUrl.includes('bsky.app'))) return false;
+      return true;
+    });
 
     let mentionsToShow;
     if (hasBuildTimeSection) {