experiment(PodcastPlayerView): add Retry button to failedView, clear pollingTask on failure

Marks/Views/PodcastPlayerView.swift

@@ -97,6 +97,7 @@ final class PodcastPlayerViewModel {
                         let errMsg = job.error ?? "Generation failed"
                         Analytics.track("podcast.failed", ["url": articleUrl, "error": errMsg])
                         phase = .failed(errMsg)
+                        pollingTask = nil
                         return
                     }
                     try await Task.sleep(for: .seconds(3))
@@ -105,6 +106,7 @@ final class PodcastPlayerViewModel {
             } catch {
                 Analytics.track("podcast.failed", ["url": articleUrl, "error": error.localizedDescription])
                 phase = .failed(error.localizedDescription)
+                pollingTask = nil
             }
         }
     }
@@ -434,6 +436,18 @@ struct PodcastPlayerView: View {
                 .font(.system(size: 14))
                 .foregroundStyle(.secondary)
                 .multilineTextAlignment(.center)
+            Button {
+                vm.start(articleUrl: articleUrl, articleTitle: articleTitle, claude: claude)
+            } label: {
+                Label("Retry", systemImage: "arrow.clockwise")
+                    .font(.system(size: 15, weight: .semibold))
+                    .foregroundStyle(.white)
+                    .padding(.horizontal, 24)
+                    .padding(.vertical, 10)
+                    .background(Color.blue)
+                    .clipShape(Capsule())
+            }
+            .padding(.top, 4)
         }
     }