feat: brain live search — results appear as you type (300ms debounce)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

frontend-v2/src/lib/pages/brain/AtelierBrainPage.svelte

@@ -208,8 +208,13 @@
     if (e.key === 'Enter' && !e.shiftKey) { e.preventDefault(); capture(); }
   }
 
-  function handleSearchKey(e: KeyboardEvent) {
-    if (e.key === 'Enter') search();
+  let searchTimer: ReturnType<typeof setTimeout>;
+
+  function handleSearchInput() {
+    clearTimeout(searchTimer);
+    searchTimer = setTimeout(() => {
+      search();
+    }, 300);
   }
 
   // Poll for pending items
@@ -345,7 +350,7 @@
           class="search-input"
           placeholder="Search your brain..."
           bind:value={searchQuery}
-          onkeydown={handleSearchKey}
+          oninput={handleSearchInput}
         />
         {#if searchQuery}
           <button class="search-clear" onclick={() => { searchQuery = ''; loadItems(); }}>