feat(BookmarkRow): adopt Dynamic Type, move cache stat off render path, safer delete

Apply WWDC26 design-brief fixes to the bookmark list reading surface:

- Dynamic Type: replace fixed .system(size:) points with text styles
  (title .headline, domain/date .footnote, summary .subheadline, tags
  .caption, podcast glyph .title3). Rows now scale and wrap with the
  user's text-size setting instead of staying fixed.
- Perf: podcastCached was a FileManager.fileExists stat evaluated inside
  body — i.e. per row, per scroll frame. Move it to @State populated by a
  .task(id:) that stats off the main actor, once per appearance.
- Forgiveness: destructive trailing swipe is now allowsFullSwipe: false so
  a single fling can't permanently delete; requires tapping the button.

Adds docs/design-wwdc26.md (consolidated brief + codebase audit).

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

Marks/Views/BookmarkListRow.swift

@@ -23,7 +23,9 @@ struct BookmarkListRow: View {
         .onTapGesture { onOpen() }
         .listRowInsets(EdgeInsets(top: 0, leading: 16, bottom: 0, trailing: 16))
         .listRowSeparator(.visible)
-        .swipeActions(edge: .trailing, allowsFullSwipe: true) {
+        // Delete is destructive and not undoable — require an explicit tap on the
+        // revealed button rather than letting a single full swipe delete instantly.
+        .swipeActions(edge: .trailing, allowsFullSwipe: false) {
             Button(role: .destructive) {
                 Task { await viewModel.delete(bookmark) }
             } label: {

Marks/Views/BookmarkRow.swift

@@ -6,6 +6,7 @@ struct BookmarkRow: View {
     var onPodcast: (() -> Void)? = nil
 
     @State private var podcastTapCount = 0
+    @State private var podcastCached = false
 
     var body: some View {
         VStack(alignment: .leading, spacing: 6) {
@@ -23,7 +24,7 @@ struct BookmarkRow: View {
 
                 VStack(alignment: .leading, spacing: 4) {
                     Text(bookmark.displayTitle)
-                        .font(.system(size: 17, weight: .semibold))
+                        .font(.headline)
                         .foregroundStyle(.primary)
                         .lineLimit(2)
                         .fixedSize(horizontal: false, vertical: true)
@@ -33,7 +34,7 @@ struct BookmarkRow: View {
                         Text("·")
                         Text(bookmark.dateAdded, style: .relative)
                     }
-                    .font(.system(size: 13))
+                    .font(.footnote)
                     .foregroundStyle(.secondary)
                 }
 
@@ -45,7 +46,7 @@ struct BookmarkRow: View {
                         onPodcast()
                     } label: {
                         Image(systemName: podcastCached ? "headphones.circle.fill" : "headphones.circle")
-                            .font(.system(size: 20))
+                            .font(.title3)
                             .foregroundStyle(podcastCached ? .blue : Color(.systemGray3))
                     }
                     .buttonStyle(.plain)
@@ -56,7 +57,7 @@ struct BookmarkRow: View {
 
             if let summary = bookmark.aiSummary {
                 Text(summary)
-                    .font(.system(size: 14))
+                    .font(.subheadline)
                     .italic()
                     .foregroundStyle(.secondary)
                     .lineLimit(2)
@@ -68,7 +69,7 @@ struct BookmarkRow: View {
                     HStack(spacing: 6) {
                         ForEach(effectiveTags, id: \.self) { tag in
                             Text(tag)
-                                .font(.system(size: 12, weight: .medium))
+                                .font(.caption.weight(.medium))
                                 .foregroundStyle(.secondary)
                                 .padding(.horizontal, 8)
                                 .padding(.vertical, 3)
@@ -97,10 +98,12 @@ struct BookmarkRow: View {
                 .frame(height: 2)
             }
         }
-    }
-
-    private var podcastCached: Bool {
-        FileManager.default.fileExists(atPath: ClaudeService.cachedPodcastURL(for: bookmark.url).path)
+        .task(id: bookmark.url) {
+            // Stat the podcast cache off the render path: once per appearance
+            // (and when the URL changes), not on every `body` recomputation.
+            let path = ClaudeService.cachedPodcastURL(for: bookmark.url).path
+            podcastCached = await Task.detached { FileManager.default.fileExists(atPath: path) }.value
+        }
     }
 
     private var effectiveTags: [String] {