feat: brain detail sheet — screenshot for links, editable notes, spelling fix

- Link detail: shows screenshot image (clickable to open URL), URL, summary, tags
- Note detail: click note text to edit, save/cancel buttons
- Notes: AI now fixes spelling/grammar instead of rewriting
- AI returns corrected_text field for notes, worker replaces raw_content
- Removed verbose meta grid (folder/confidence/status/saved)
- Folder shown as a pill badge in meta line

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

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

@@ -401,12 +401,25 @@
         </button>
       </div>
 
-      {#if selectedItem.url}
-        <a class="detail-url" href={selectedItem.url} target="_blank" rel="noopener">{selectedItem.url}</a>
+      <!-- Link: show screenshot + URL + tags -->
+      {#if selectedItem.type === 'link'}
+        {#if selectedItem.assets?.some(a => a.asset_type === 'screenshot')}
+          <a class="detail-screenshot" href={selectedItem.url} target="_blank" rel="noopener">
+            <img src="/api/brain/storage/{selectedItem.id}/screenshot/screenshot.png" alt="" />
+          </a>
+        {/if}
+
+        {#if selectedItem.url}
+          <a class="detail-url" href={selectedItem.url} target="_blank" rel="noopener">{selectedItem.url}</a>
+        {/if}
+
+        {#if selectedItem.summary}
+          <div class="detail-summary">{selectedItem.summary}</div>
+        {/if}
       {/if}
 
+      <!-- Note: editable content -->
       {#if selectedItem.type === 'note'}
-        <!-- Editable note content -->
         <div class="detail-content">
           {#if editingNote}
             <textarea
@@ -426,10 +439,6 @@
         </div>
       {/if}
 
-      {#if selectedItem.summary}
-        <div class="detail-summary">{selectedItem.summary}</div>
-      {/if}
-
       {#if selectedItem.tags && selectedItem.tags.length > 0}
         <div class="detail-tags">
           {#each selectedItem.tags as tag}
@@ -439,7 +448,7 @@
       {/if}
 
       <div class="detail-meta-line">
-        {#if selectedItem.folder}<span>{selectedItem.folder}</span>{/if}
+        {#if selectedItem.folder}<span class="meta-folder-pill">{selectedItem.folder}</span>{/if}
         <span>{formatDate(selectedItem.created_at)}</span>
       </div>
 
@@ -755,13 +764,27 @@
   .close-btn:hover { background: rgba(35,26,17,0.08); color: #1e1812; }
   .close-btn svg { width: 20px; height: 20px; }
 
+  .detail-screenshot {
+    display: block; border-radius: 14px; overflow: hidden;
+    margin-bottom: 16px; border: 1px solid rgba(35,26,17,0.08);
+  }
+  .detail-screenshot img {
+    width: 100%; height: auto; display: block; max-height: 300px; object-fit: cover;
+  }
+  .detail-screenshot:hover { opacity: 0.95; }
+
   .detail-url {
-    display: block; font-size: 0.88rem; color: #8c7b69;
-    margin-bottom: 16px; word-break: break-all;
+    display: block; font-size: 0.85rem; color: #8c7b69;
+    margin-bottom: 14px; word-break: break-all;
     text-decoration: none;
   }
   .detail-url:hover { color: #1e1812; text-decoration: underline; }
 
+  .meta-folder-pill {
+    background: rgba(35,26,17,0.06); padding: 2px 10px;
+    border-radius: 999px; font-weight: 600;
+  }
+
   .detail-content {
     margin-bottom: 20px;
   }