Sink seen/read stories, fix F1 matching, drop East Africa pill

- Sink already-seen and read stories to the bottom of the feed (new SeenStory
  model + per-load snapshot so order is stable while scrolling and refreshes
  sink what you've seen) so fresh content surfaces.
- F1 matching: clear F1 headline OR a majority of F1-feed sources, replacing the
  broad keyword list that leaked crypto in (fia -> "deFIAnt"). Dropped unused
  matchSources path.
- Remove the East Africa pill.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Jarvis/Views/Home/SignalFeedView.swift

@@ -25,10 +25,14 @@ struct SignalFeedView: View {
     @Query private var cachedArticles: [CachedArticle]
     @Query private var readStories: [ReadStory]
     @Query private var savedStories: [SavedStory]
+    @Query private var seenStories: [SeenStory]
     @State private var showFeeds = false
     @State private var showSettings = false
     @State private var selectedInterest: Interest? = nil
     @State private var shareStory: StorySummary?
+    /// Snapshot of already-seen story ids, captured per load so the order stays
+    /// stable while scrolling (and refreshes to sink newly-seen ones).
+    @State private var seenSnapshot: Set<String> = []
 
     /// Stories that have full article content cached → eligible for the green dot.
     private var cachedStoryIds: Set<String> { Set(cachedArticles.map(\.storyId)) }
@@ -45,16 +49,36 @@ struct SignalFeedView: View {
         } else {
             base = []
         }
-        guard let interest = selectedInterest else {
+
+        let filtered: [StorySummary]
+        if let interest = selectedInterest {
+            if interest.id == "f1" {
+                filtered = base.filter(interest.matches)
+            } else {
+                // Other pills (incl. Tech/Finance) exclude F1 (backend mis-tags it).
+                filtered = base.filter { interest.matches($0) && !Interest.f1.matches($0) }
+            }
+        } else {
             // "All" is news-only: F1 lives solely under its own pill.
-            return base.filter { !Interest.f1.matches($0) }
+            filtered = base.filter { !Interest.f1.matches($0) }
         }
-        if interest.id == "f1" {
-            return base.filter(interest.matches)
-        }
-        // Every other pill (incl. Tech/Finance) excludes F1, since the backend
-        // mis-tags F1 stories into finance/tech/politics.
-        return base.filter { interest.matches($0) && !Interest.f1.matches($0) }
+
+        // Sink stories you've already read or seen (in a prior load) so fresh
+        // content surfaces and you stop seeing the same articles. Uses a per-load
+        // snapshot so the order is stable while you scroll.
+        let demoted = readStoryIds.union(seenSnapshot)
+        let fresh = filtered.filter { !demoted.contains($0.id) }
+        let old = filtered.filter { demoted.contains($0.id) }
+        return fresh + old
+    }
+
+    private func captureSeenSnapshot() { seenSnapshot = Set(seenStories.map(\.id)) }
+
+    private func markSeen(_ s: StorySummary) {
+        let id = s.id
+        guard !seenStories.contains(where: { $0.id == id }) else { return }
+        modelContext.insert(SeenStory(id: id))
+        try? modelContext.save()
     }
 
     var body: some View {
@@ -218,6 +242,7 @@ struct SignalFeedView: View {
                     .listRowBackground(Color.black)
                     .listRowSeparator(.hidden)
                     .onAppear {
+                        markSeen(story)
                         if story.id == displayStories.last?.id {
                             Task { await store.loadMore() }
                         }
@@ -255,7 +280,9 @@ struct SignalFeedView: View {
         .listStyle(.plain)
         .scrollContentBackground(.hidden)
         .background(Color.black)
+        .onAppear { captureSeenSnapshot() }
         .refreshable {
+            captureSeenSnapshot()           // sink what you've already seen
             await store.loadStories(refresh: true)
         }
     }