fix(knowledge): replace IntersectionObserver with scroll event; increase card height

- Swap IntersectionObserver (race-prone, fired immediately on creation)
  for a passive scroll listener on the grid container — eliminates
  duplicate page loads caused by observer re-creation after DOM updates
- Increase card min-height 100px → 160px so tags + snippet are visible
- Increase snippet line-clamp 3 → 4 for more content preview

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

frontend/src/views/KnowledgeView.vue

@@ -1,5 +1,5 @@
 <script setup lang="ts">
-import { ref, watch, onMounted, onUnmounted, nextTick, watchEffect } from "vue";
+import { ref, watch, onMounted, onUnmounted } from "vue";
 import { useRouter } from "vue-router";
 import { apiGet, apiPatch } from "@/api/client";
 import { fmtCompact } from "@/utils/dateFormat";
@@ -244,23 +244,16 @@ function formatDate(iso: string): string {
 
 // ─── Infinite scroll ──────────────────────────────────────────────────────────
 
-const sentinelEl = ref<HTMLElement | null>(null);
 const cardGridEl = ref<HTMLElement | null>(null);
-let scrollObserver: IntersectionObserver | null = null;
 
-function setupScrollObserver() {
-  if (scrollObserver) scrollObserver.disconnect();
-  if (!sentinelEl.value || !cardGridEl.value) return;
-  scrollObserver = new IntersectionObserver(
-    (entries) => {
-      if (entries[0].isIntersecting && !loading.value && items.value.length < total.value) {
-        page.value++;
-        fetchItems();
-      }
-    },
-    { root: cardGridEl.value, rootMargin: "200px" }
-  );
-  scrollObserver.observe(sentinelEl.value);
+function onGridScroll() {
+  const el = cardGridEl.value;
+  if (!el || loading.value || items.value.length >= total.value) return;
+  const nearBottom = el.scrollHeight - el.scrollTop - el.clientHeight < 300;
+  if (nearBottom) {
+    page.value++;
+    fetchItems();
+  }
 }
 
 // ─── Lifecycle ────────────────────────────────────────────────────────────────
@@ -269,16 +262,10 @@ onMounted(() => {
   fetchItems(true);
   fetchTags();
   fetchTodayBar();
-  nextTick(() => setupScrollObserver());
 });
 
 onUnmounted(() => {
   if (searchDebounce) clearTimeout(searchDebounce);
-  scrollObserver?.disconnect();
-});
-
-watchEffect(() => {
-  if (sentinelEl.value && cardGridEl.value) setupScrollObserver();
 });
 </script>
 
@@ -380,8 +367,8 @@ watchEffect(() => {
           <p v-else class="empty-hint">Start by creating a note, saving a person or place, or making a list.</p>
         </div>
 
-        <!-- Card grid (sentinel lives inside so IntersectionObserver root works) -->
-        <div v-else ref="cardGridEl" class="card-grid">
+        <!-- Card grid -->
+        <div v-else ref="cardGridEl" class="card-grid" @scroll.passive="onGridScroll">
           <div
             v-for="item in items"
             :key="item.id"
@@ -446,10 +433,8 @@ watchEffect(() => {
             </div>
           </div>
 
-          <!-- Sentinel after all cards — IntersectionObserver triggers next page load -->
-          <div ref="sentinelEl" class="scroll-sentinel">
-            <span v-if="loading && items.length > 0" class="sentinel-loading">Loading…</span>
-          </div>
+          <!-- Loading indicator when fetching additional pages -->
+          <div v-if="loading && items.length > 0" class="load-more-indicator">Loading…</div>
         </div>
       </div>
 
@@ -730,7 +715,7 @@ watchEffect(() => {
   display: flex;
   flex-direction: column;
   gap: 8px;
-  min-height: 100px;
+  min-height: 160px;
   overflow: hidden;
 }
 .k-card:hover {
@@ -777,7 +762,7 @@ watchEffect(() => {
   font-size: 0.8rem;
   color: var(--color-muted);
   display: -webkit-box;
-  -webkit-line-clamp: 3;
+  -webkit-line-clamp: 4;
   -webkit-box-orient: vertical;
   overflow: hidden;
   line-height: 1.45;
@@ -877,15 +862,11 @@ watchEffect(() => {
 }
 .empty-hint { font-size: 0.85rem; opacity: 0.7; }
 
-/* ── Infinite scroll sentinel ────────────────────────────── */
-.scroll-sentinel {
-  grid-column: 1 / -1; /* span all columns so it's not a card-sized slot */
-  height: 40px;
-  display: flex;
-  align-items: center;
-  justify-content: center;
-}
-.sentinel-loading {
+/* ── Load more indicator ─────────────────────────────────── */
+.load-more-indicator {
+  grid-column: 1 / -1;
+  padding: 16px;
+  text-align: center;
   font-size: 0.8rem;
   color: var(--color-muted);
 }