feat(podcasts): #8 episode detail sheet (source, played state, actions)

- New EpisodeDetailView: title, source domain, created date, played badge,
  and per-episode actions — Play/Pause, Mark Played/Unplayed, Open Source,
  Share, Delete — all routed through the PodcastLibrary store so the badge
  stays in sync.
- Reachable by tapping a row (or "Episode Details" in the context menu) in the
  Podcasts tab, and by tapping a row in the episode picker.

Note: AI summary is intentionally omitted for now — it's keyed by bookmark id
(not URL), so surfacing it would recouple the deliberately-decoupled Podcasts
tab to BookmarksViewModel. Open Source uses Safari rather than the in-app
browser to avoid sheet-stacking. Both are noted as follow-ups on issue #8.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Marks/Views/PodcastPlayerView.swift

@@ -800,6 +800,7 @@ struct PodcastLibraryView: View {
 
     @State private var library = PodcastLibrary.shared
     @State private var showFullPlayer = false
+    @State private var detailEntry: PodcastEntry?
 
     var body: some View {
         NavigationStack {
@@ -856,6 +857,9 @@ struct PodcastLibraryView: View {
                     stopOnDismiss: false
                 )
             }
+            .sheet(item: $detailEntry) { entry in
+                EpisodeDetailView(entry: entry, vm: vm, claude: claude)
+            }
         }
         .onAppear { library.reload() }
         // When the current episode changes (finished, advanced, or stopped),
@@ -896,6 +900,8 @@ struct PodcastLibraryView: View {
             .buttonStyle(.plain)
         }
         .padding(.vertical, 6)
+        .contentShape(Rectangle())
+        .onTapGesture { detailEntry = entry }
         .swipeActions(edge: .leading) {
             Button {
                 setPlayed(entry, !entry.isPlayed)
@@ -922,6 +928,11 @@ struct PodcastLibraryView: View {
                 Label(isCurrent(entry) && vm.isPlaying ? "Pause" : "Play",
                       systemImage: isCurrent(entry) && vm.isPlaying ? "pause" : "play")
             }
+            Button {
+                detailEntry = entry
+            } label: {
+                Label("Episode Details", systemImage: "info.circle")
+            }
             Button {
                 setPlayed(entry, !entry.isPlayed)
             } label: {
@@ -970,6 +981,7 @@ struct EpisodePickerView: View {
     let claude: ClaudeService
 
     @State private var entries: [PodcastEntry] = []
+    @State private var detailEntry: PodcastEntry?
     @Environment(\.dismiss) private var dismiss
 
     var body: some View {
@@ -1005,6 +1017,8 @@ struct EpisodePickerView: View {
                         .buttonStyle(.plain)
                     }
                     .padding(.vertical, 6)
+                    .contentShape(Rectangle())
+                    .onTapGesture { detailEntry = entry }
                     .swipeActions(edge: .trailing, allowsFullSwipe: true) {
                         Button(role: .destructive) { deleteEntry(entry) } label: {
                             Label("Delete", systemImage: "trash")
@@ -1020,6 +1034,9 @@ struct EpisodePickerView: View {
                     Button("Done") { dismiss() }
                 }
             }
+            .sheet(item: $detailEntry) { entry in
+                EpisodeDetailView(entry: entry, vm: vm, claude: claude)
+            }
         }
         .onAppear { entries = PodcastIndex.find(for: bookmark.url) }
     }
@@ -1030,3 +1047,103 @@ struct EpisodePickerView: View {
         if vm.currentArticleUrl == entry.articleUrl { vm.stop() }
     }
 }
+
+// MARK: - Episode detail
+
+/// Detail sheet for a single episode: reconnects the podcast to its source
+/// bookmark and gathers per-episode actions (play, mark played, open source,
+/// share, delete) in one place.
+struct EpisodeDetailView: View {
+    let entry: PodcastEntry
+    let vm: PodcastPlayerViewModel
+    let claude: ClaudeService
+
+    @Environment(\.dismiss) private var dismiss
+    @Environment(\.openURL) private var openURL
+    @State private var library = PodcastLibrary.shared
+
+    private var isCurrent: Bool { vm.currentArticleUrl == entry.articleUrl }
+    private var isPlayed: Bool {
+        library.entries.first { $0.articleUrl == entry.articleUrl }?.isPlayed ?? entry.isPlayed
+    }
+    private var sourceURL: URL? { URL(string: entry.parentBookmarkUrl ?? entry.articleUrl) }
+    private var domain: String { URL(string: entry.articleUrl)?.host ?? entry.articleUrl }
+
+    var body: some View {
+        NavigationStack {
+            List {
+                Section {
+                    VStack(alignment: .leading, spacing: 8) {
+                        Text(entry.title ?? entry.articleUrl)
+                            .font(.system(size: 20, weight: .semibold))
+                        Label(domain, systemImage: "link")
+                            .font(.subheadline)
+                            .foregroundStyle(.secondary)
+                            .lineLimit(1)
+                        HStack(spacing: 12) {
+                            Label(entry.createdAt.formatted(date: .abbreviated, time: .omitted),
+                                  systemImage: "calendar")
+                            if isPlayed {
+                                Label("Played", systemImage: "checkmark.circle.fill")
+                                    .foregroundStyle(.green)
+                            }
+                        }
+                        .font(.caption)
+                        .foregroundStyle(.secondary)
+                    }
+                    .padding(.vertical, 4)
+                }
+
+                Section {
+                    Button {
+                        if isCurrent {
+                            vm.togglePlayPause()
+                        } else {
+                            vm.start(articleUrl: entry.articleUrl,
+                                     articleTitle: entry.title ?? "", claude: claude)
+                        }
+                    } label: {
+                        Label(isCurrent && vm.isPlaying ? "Pause" : "Play",
+                              systemImage: isCurrent && vm.isPlaying ? "pause.fill" : "play.fill")
+                    }
+                    Button {
+                        library.setPlayed(entry.articleUrl, !isPlayed)
+                    } label: {
+                        Label(isPlayed ? "Mark as Unplayed" : "Mark as Played",
+                              systemImage: isPlayed ? "circle" : "checkmark.circle")
+                    }
+                }
+
+                if let sourceURL {
+                    Section {
+                        Button {
+                            openURL(sourceURL)
+                        } label: {
+                            Label("Open Source", systemImage: "safari")
+                        }
+                        ShareLink(item: sourceURL) {
+                            Label("Share Episode", systemImage: "square.and.arrow.up")
+                        }
+                    }
+                }
+
+                Section {
+                    Button(role: .destructive) {
+                        library.remove(entry.articleUrl)
+                        if vm.currentArticleUrl == entry.articleUrl { vm.stop() }
+                        dismiss()
+                    } label: {
+                        Label("Delete Episode", systemImage: "trash")
+                    }
+                }
+            }
+            .navigationTitle("Episode")
+            .navigationBarTitleDisplayMode(.inline)
+            .toolbar {
+                ToolbarItem(placement: .topBarTrailing) {
+                    Button("Done") { dismiss() }
+                }
+            }
+        }
+    }
+}