Feed resilience, clearer empty states, and read/unread

- Don't blank the feed on refresh: keep current stories until new data
  arrives, and ignore benign URLError.cancelled (-999) so a network blip
  no longer wipes the list. Coalesce WebSocket story.created bursts into a
  single debounced refresh.
- Empty state now distinguishes polling, couldn't-reach-server (with the
  error + host + Retry), offline, and genuinely-empty.
- Track read stories in SwiftData (ReadStory); mark a story read when opened
  and drop/dim its signal stripe across the feed and Latest/Saved/Search.

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

Jarvis/Views/SecondaryTabs.swift

@@ -34,12 +34,15 @@ private struct TabHeader: View {
 private struct StoryList: View {
     let stories: [StorySummary]
     let cachedIds: Set<String>
+    var readIds: Set<String> = []
     var body: some View {
         ScrollView {
             LazyVStack(spacing: 0) {
                 ForEach(stories) { story in
                     NavigationLink(value: story) {
-                        StoryRowView(story: story, isCached: cachedIds.contains(story.id))
+                        StoryRowView(story: story,
+                                     isCached: cachedIds.contains(story.id),
+                                     isRead: readIds.contains(story.id))
                     }
                     .buttonStyle(.plain)
                 }
@@ -53,6 +56,7 @@ private struct StoryList: View {
 struct LatestView: View {
     @EnvironmentObject var store: StoryStore
     @Query private var cachedArticles: [CachedArticle]
+    @Query private var readStories: [ReadStory]
 
     private var latest: [StorySummary] {
         store.stories.sorted { $0.createdAt > $1.createdAt }
@@ -65,7 +69,8 @@ struct LatestView: View {
                 VStack(spacing: 0) {
                     TabHeader(title: "Latest")
                     Divider().overlay(Palette.hairline)
-                    StoryList(stories: latest, cachedIds: Set(cachedArticles.map(\.storyId)))
+                    StoryList(stories: latest, cachedIds: Set(cachedArticles.map(\.storyId)),
+                              readIds: Set(readStories.map(\.id)))
                 }
             }
             .navigationBarHidden(true)
@@ -80,6 +85,7 @@ struct LatestView: View {
 struct SavedView: View {
     @Query private var cachedStories: [CachedStory]
     @Query private var cachedArticles: [CachedArticle]
+    @Query private var readStories: [ReadStory]
 
     private var stories: [StorySummary] {
         cachedStories.map(StorySummary.init(cached:)).sorted { $0.signalScore > $1.signalScore }
@@ -102,7 +108,8 @@ struct SavedView: View {
                         }
                         .frame(maxWidth: .infinity, maxHeight: .infinity)
                     } else {
-                        StoryList(stories: stories, cachedIds: Set(cachedArticles.map(\.storyId)))
+                        StoryList(stories: stories, cachedIds: Set(cachedArticles.map(\.storyId)),
+                                  readIds: Set(readStories.map(\.id)))
                     }
                 }
             }
@@ -118,6 +125,7 @@ struct SavedView: View {
 struct SearchView: View {
     @EnvironmentObject var store: StoryStore
     @Query private var cachedArticles: [CachedArticle]
+    @Query private var readStories: [ReadStory]
     @State private var query = ""
 
     private var results: [StorySummary] {
@@ -141,7 +149,8 @@ struct SearchView: View {
                     } else if results.isEmpty {
                         placeholder("No matches for “\(query)”")
                     } else {
-                        StoryList(stories: results, cachedIds: Set(cachedArticles.map(\.storyId)))
+                        StoryList(stories: results, cachedIds: Set(cachedArticles.map(\.storyId)),
+                                  readIds: Set(readStories.map(\.id)))
                     }
                 }
             }