fix(memory-echo): feedback-adjusted thresholds and remove duplicate close button

- Thumbs down now increases the similarity threshold by +0.15 for the
  notes involved, making it harder for irrelevant connections to reappear
- Thumbs up slightly lowers the threshold by -0.05, boosting similar
  future connections
- Remove duplicate close button in ComparisonModal (kept only the
  native Dialog close button)
- Normalize all embeddings to same model/dimension (2560) to fix
  random similarity scores caused by mixed embedding models

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

keep-notes/components/comparison-modal.tsx

@@ -3,7 +3,7 @@
 import { useState } from 'react'
 import { Dialog, DialogContent } from '@/components/ui/dialog'
 import { Button } from '@/components/ui/button'
-import { X, Sparkles, ThumbsUp, ThumbsDown } from 'lucide-react'
+import { Sparkles, ThumbsUp, ThumbsDown, GitMerge } from 'lucide-react'
 import { cn } from '@/lib/utils'
 import { Note } from '@/lib/types'
 import { useLanguage } from '@/lib/i18n/LanguageProvider'
@@ -14,6 +14,7 @@ interface ComparisonModalProps {
   notes: Array<Partial<Note>>
   similarity?: number
   onOpenNote?: (noteId: string) => void
+  onMergeNotes?: (noteIds: string[]) => void
 }
 
 export function ComparisonModal({
@@ -21,14 +22,26 @@ export function ComparisonModal({
   onClose,
   notes,
   similarity,
-  onOpenNote
+  onOpenNote,
+  onMergeNotes
 }: ComparisonModalProps) {
   const { t } = useLanguage()
   const [feedback, setFeedback] = useState<'thumbs_up' | 'thumbs_down' | null>(null)
 
   const handleFeedback = async (type: 'thumbs_up' | 'thumbs_down') => {
     setFeedback(type)
-    // TODO: Send feedback to backend
+    try {
+      const noteIds = notes.map(n => n.id).filter(Boolean) as string[]
+      if (noteIds.length >= 2) {
+        await fetch('/api/ai/echo', {
+          method: 'POST',
+          headers: { 'Content-Type': 'application/json' },
+          body: JSON.stringify({ action: 'feedback', noteIds, feedback: type })
+        })
+      }
+    } catch {
+      // silent — feedback is best-effort
+    }
     setTimeout(() => {
       onClose()
     }, 500)
@@ -76,15 +89,9 @@ export function ComparisonModal({
               </p>
             </div>
           </div>
-          <button
-            onClick={onClose}
-            className="text-gray-500 hover:text-gray-700 dark:hover:text-gray-300"
-          >
-            <X className="h-6 w-6" />
-          </button>
         </div>
 
-        {/* AI Insight Section - Optional for now */}
+        {/* AI Insight Section */}
         {similarityPercentage >= 80 && (
           <div className="px-6 py-4 bg-amber-50 dark:bg-amber-950/20 border-b dark:border-zinc-700">
             <div className="flex items-start gap-2">
@@ -137,13 +144,13 @@ export function ComparisonModal({
           })}
         </div>
 
-        {/* Footer - Feedback */}
+        {/* Footer - Feedback + Actions */}
         <div className="px-6 py-4 border-t dark:border-zinc-700 bg-gray-50 dark:bg-zinc-800/50">
           <div className="flex items-center justify-between">
-            <p className="text-sm text-gray-600 dark:text-gray-400">
-              {t('memoryEcho.comparison.helpfulQuestion')}
-            </p>
             <div className="flex items-center gap-2">
+              <p className="text-sm text-gray-600 dark:text-gray-400">
+                {t('memoryEcho.comparison.helpfulQuestion')}
+              </p>
               <Button
                 size="sm"
                 variant={feedback === 'thumbs_up' ? 'default' : 'outline'}
@@ -167,6 +174,21 @@ export function ComparisonModal({
                 {t('memoryEcho.comparison.notHelpful')}
               </Button>
             </div>
+
+            {onMergeNotes && notes.length >= 2 && (
+              <Button
+                size="sm"
+                className="bg-purple-600 hover:bg-purple-700 text-white"
+                onClick={() => {
+                  const noteIds = notes.map(n => n.id).filter(Boolean) as string[]
+                  onMergeNotes(noteIds)
+                  onClose()
+                }}
+              >
+                <GitMerge className="h-4 w-4 mr-2" />
+                {t('memoryEcho.editorSection.mergeAll')}
+              </Button>
+            )}
           </div>
         </div>
       </DialogContent>