Persist author cache to disk for instant channel info across restarts

Back the in-memory authorCache with a JSON file in ~/Library/Caches/AuthorCache/.
Disk is lazy-loaded on first lookup and saved asynchronously on each cache update.
Capped at 500 entries to prevent unbounded growth.

- Cache author data from video detail API responses (PlayerService, VideoInfoView)
- Replace ChannelView's private CachedChannelHeader with shared CachedChannelData
- Enrich author with cached avatar/subscriber count in VideoChannelRow, TVDetailsPanel, VideoInfoView

Yattee/Views/Channel/ChannelView.swift

@@ -8,25 +8,6 @@
 import SwiftUI
 import NukeUI
 
-/// Cached channel data for showing header immediately while loading.
-private struct CachedChannelHeader {
-    let name: String
-    let thumbnailURL: URL?
-    let bannerURL: URL?
-
-    init(from subscription: Subscription) {
-        name = subscription.name
-        thumbnailURL = subscription.avatarURL
-        bannerURL = subscription.bannerURL
-    }
-
-    init(from recentChannel: RecentChannel) {
-        name = recentChannel.name
-        thumbnailURL = recentChannel.thumbnailURLString.flatMap { URL(string: $0) }
-        bannerURL = nil  // RecentChannel doesn't store banner
-    }
-}
-
 struct ChannelView: View {
     @Environment(\.appEnvironment) private var appEnvironment
     @Environment(\.horizontalSizeClass) private var horizontalSizeClass
@@ -52,7 +33,7 @@ struct ChannelView: View {
     @State private var showingUnsubscribeConfirmation = false
     @State private var scrollOffset: CGFloat = 0
     @State private var scrollToTop: Bool = false
-    @State private var cachedHeader: CachedChannelHeader?
+    @State private var cachedHeader: CachedChannelData?
 
     // View options (persisted)
     @AppStorage("channel.layout") private var layout: VideoListLayout = .list
@@ -393,7 +374,7 @@ struct ChannelView: View {
 
     /// Shows cached header with a spinner below while loading full channel data.
     @ViewBuilder
-    private func loadingContent(_ cached: CachedChannelHeader) -> some View {
+    private func loadingContent(_ cached: CachedChannelData) -> some View {
         GeometryReader { geometry in
             ScrollView {
                 LazyVStack(spacing: 0) {
@@ -1526,11 +1507,7 @@ struct ChannelView: View {
         isSubscribed = subscription != nil
 
         // Load cached header data for immediate display
-        if let subscription {
-            cachedHeader = CachedChannelHeader(from: subscription)
-        } else if let recentChannel = appEnvironment.dataManager.recentChannelEntry(forChannelID: channelID) {
-            cachedHeader = CachedChannelHeader(from: recentChannel)
-        }
+        cachedHeader = CachedChannelData.load(for: channelID, using: appEnvironment.dataManager)
 
         // Fetch channel and videos independently to handle partial failures gracefully
         async let channelTask: Result<Channel, Error> = await {
@@ -1576,7 +1553,7 @@ struct ChannelView: View {
                         id: ChannelID(source: source, channelID: channelID),
                         name: cached.name,
                         description: nil,
-                        subscriberCount: nil,
+                        subscriberCount: cached.subscriberCount,
                         thumbnailURL: cached.thumbnailURL,
                         bannerURL: cached.bannerURL
                     )

Yattee/Views/Components/VideoInfoComponents.swift

@@ -92,6 +92,8 @@ struct VideoStatsRow: View {
 
 /// Displays channel info with avatar, name, subscriber count, and context menu.
 struct VideoChannelRow: View {
+    @Environment(\.appEnvironment) private var appEnvironment
+
     let author: Author
     let source: ContentSource
     let yatteeServerURL: URL?
@@ -101,6 +103,12 @@ struct VideoChannelRow: View {
     var showSubscriberCount: Bool = true
     var isLoadingDetails: Bool = false
 
+    /// Author enriched with cached channel data (avatar, subscriber count) from local stores.
+    private var enrichedAuthor: Author {
+        guard let dataManager = appEnvironment?.dataManager else { return author }
+        return author.enriched(using: dataManager)
+    }
+
     var body: some View {
         HStack(spacing: 12) {
             if let onChannelTap {
@@ -129,21 +137,21 @@ struct VideoChannelRow: View {
     private var channelContent: some View {
         HStack(spacing: 10) {
             ChannelAvatarView(
-                author: author,
+                author: enrichedAuthor,
                 size: 40,
                 yatteeServerURL: yatteeServerURL,
                 source: source
             )
 
             VStack(alignment: .leading, spacing: 2) {
-                Text(author.name)
+                Text(enrichedAuthor.name)
                     .font(.subheadline)
                     .fontWeight(.medium)
                     .lineLimit(1)
 
                 if showSubscriberCount {
                     Group {
-                        if let subscribers = author.formattedSubscriberCount {
+                        if let subscribers = enrichedAuthor.formattedSubscriberCount {
                             Text(subscribers)
                         } else if isLoadingDetails && video.supportsAPIStats {
                             Text("1.2M subscribers")

Yattee/Views/Player/tvOS/TVDetailsPanel.swift

@@ -152,10 +152,17 @@ struct TVDetailsPanel: View {
 
     // MARK: - Channel Row
 
+    /// Author enriched with cached channel data (avatar, subscriber count) from local stores.
+    private var enrichedAuthor: Author? {
+        guard let video else { return nil }
+        guard let dataManager = appEnvironment?.dataManager else { return video.author }
+        return video.author.enriched(using: dataManager)
+    }
+
     private var channelRow: some View {
         HStack(spacing: 16) {
             // Channel avatar
-            if let thumbnailURL = video?.author.thumbnailURL {
+            if let thumbnailURL = enrichedAuthor?.thumbnailURL {
                 AsyncImage(url: thumbnailURL) { image in
                     image
                         .resizable()
@@ -179,12 +186,12 @@ struct TVDetailsPanel: View {
 
             VStack(alignment: .leading, spacing: 4) {
                 // Channel name
-                Text(video?.author.name ?? "")
+                Text(enrichedAuthor?.name ?? "")
                     .font(.headline)
                     .foregroundStyle(.white)
 
                 // Subscriber count
-                if let subscriberCount = video?.author.subscriberCount {
+                if let subscriberCount = enrichedAuthor?.subscriberCount {
                     Text("channel.subscriberCount \(CountFormatter.compact(subscriberCount))")
                         .font(.subheadline)
                         .foregroundStyle(.white.opacity(0.6))

Yattee/Views/Video/VideoInfoView.swift

@@ -765,21 +765,22 @@ struct VideoInfoView: View {
 
     /// Channel row content used in both tappable and non-tappable variants
     private func channelRowContent(for video: Video) -> some View {
-        HStack(spacing: 10) {
+        let enrichedAuthor = appEnvironment.map { video.author.enriched(using: $0.dataManager) } ?? video.author
+        return HStack(spacing: 10) {
             ChannelAvatarView(
-                author: video.author,
+                author: enrichedAuthor,
                 size: 40,
                 yatteeServerURL: yatteeServerURL,
                 source: video.authorSource
             )
 
             VStack(alignment: .leading, spacing: 2) {
-                Text(video.author.name)
+                Text(enrichedAuthor.name)
                     .font(.subheadline)
                     .fontWeight(.medium)
                     .lineLimit(1)
 
-                if let subscribers = video.author.formattedSubscriberCount {
+                if let subscribers = enrichedAuthor.formattedSubscriberCount {
                     Text(subscribers)
                         .font(.caption)
                         .foregroundStyle(.secondary)
@@ -1784,6 +1785,7 @@ struct VideoInfoView: View {
                 // Use extractURL method - just use the video part
                 let (fullVideo, _, _) = try await contentService.extractURL(originalURL, instance: instance)
                 loadedVideoDetails[videoID] = fullVideo
+                CachedChannelData.cacheAuthor(fullVideo.author)
             } catch {
                 // Fail silently - use partial video data we have
             }
@@ -1807,6 +1809,7 @@ struct VideoInfoView: View {
                 instance: instance
             )
             loadedVideoDetails[videoID] = fullVideo
+            CachedChannelData.cacheAuthor(fullVideo.author)
         } catch {
             // Fail silently - just use the partial video data we have
         }