feat: read-shelf auto-expand, stripe removal, pull-reshuffle, BG notifications

- Mark-read now immediately expands the READ shelf so the story is visible
- Orange signal stripe is fully removed (not dimmed) when isRead=true
- Pull-to-refresh clears seen snapshot → full reshuffle by signal score
- BackgroundRefreshManager fires a local notification for the top new
  high-signal story after each cache refresh; Tech/AI/HomeLab stories
  get their category in the notification title (≥65 signal threshold)

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

Jarvis/Views/Home/SignalFeedView.swift

@@ -272,9 +272,13 @@ struct SignalFeedView: View {
         .scrollContentBackground(.hidden)
         .background(Color.black)
         .animation(.snappy, value: showRead)
+        .animation(.snappy, value: readStories.count)
         .onAppear { captureSeenSnapshot() }
         .refreshable {
-            captureSeenSnapshot()           // sink what you've already seen
+            // Reshuffle: clear the seen snapshot so all stories re-rank by signal
+            // score, and any stories cached by background refresh float to the top.
+            seenSnapshot = []
+            seenTracker.ids = []
             await store.loadStories(refresh: true)
         }
     }
@@ -566,6 +570,7 @@ struct SignalFeedView: View {
         if existing?.first == nil {
             modelContext.insert(ReadStory(id: id))
             try? modelContext.save()
+            withAnimation(.snappy) { showRead = true }
         }
     }