fix: dedup log rows between API seed and websocket tail

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

hbd/server/templates/log.html

@@ -87,6 +87,7 @@
       var PAGE_SIZE = 200;
       var oldestTs = null;   // ts of the oldest loaded row (pagination cursor)
       var seq = 0;           // guards against out-of-order fetch responses
+      var newestTs = null;   // ts of the newest loaded row (dedup guard for the WS tail)
 
       function escHtml(s) {
         return String(s).replace(/&/g,'&amp;').replace(/</g,'&lt;').replace(/>/g,'&gt;').replace(/"/g,'&quot;').replace(/'/g,'&#39;');
@@ -165,6 +166,7 @@
         data.events.forEach(function (ev) {
           html += logRowHtml(ev);
           if (ev.ts != null && (oldestTs == null || ev.ts < oldestTs)) oldestTs = ev.ts;
+          if (ev.ts != null && (newestTs == null || ev.ts > newestTs)) newestTs = ev.ts;
         });
         box.insertAdjacentHTML('beforeend', html);
         if (!box.children.length) box.innerHTML = '<div class="empty">No events found.</div>';
@@ -204,6 +206,8 @@
           if (state.type !== "message" || state.history) return;
           var msg = state.data;
           if (!matchesFilters(msg)) return;
+          if (msg.ts != null && newestTs != null && msg.ts <= newestTs) return;  // already loaded via the API
+          if (msg.ts != null && (newestTs == null || msg.ts > newestTs)) newestTs = msg.ts;
           var box = document.getElementById('messages');
           var placeholder = box.querySelector('.empty');
           if (placeholder) placeholder.remove();