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>

services/brain/app/worker/tasks.py

@@ -111,6 +111,11 @@ async def _process_item(item_id: str):
             item.title = classification.get("title") or title or "Untitled"
             item.folder = classification.get("folder", "Knowledge")
             item.tags = classification.get("tags", ["reference", "read-later"])
+
+            # For notes: replace raw_content with spell-corrected version
+            corrected = classification.get("corrected_text", "")
+            if item.type == "note" and corrected and corrected.strip():
+                item.raw_content = corrected
             item.summary = classification.get("summary")
             item.confidence = classification.get("confidence", 0.0)
             item.extracted_text = extracted_text