stay and start at first attention item

mac/Sources/Byre/Chat.swift

@@ -28,6 +28,7 @@ final class ChatModel {
     private(set) var hasUnmerged = false
     @ObservationIgnored var stuck = true
     @ObservationIgnored var prepended = false
+    @ObservationIgnored var released: Int?
     @ObservationIgnored private var unmergedTimer: Task<Void, Never>?
     @ObservationIgnored private var offs: [() -> Void] = []
     @ObservationIgnored private var focusStart = true
@@ -335,6 +336,18 @@ final class ChatModel {
         return groups
     }
 
+    var held: Int? {
+        let ids = Set(attention().flatMap(\.rows))
+        guard let first = builder.root.rows.first(where: { ids.contains($0.id) })?.id, first != released else {
+            return nil
+        }
+        return first
+    }
+
+    func release() {
+        released = held ?? released
+    }
+
     func cycle(_ g: AttentionGroup) {
         let next = (cursors[g.id] ?? -1) + 1
         let i = next < g.rows.count ? next : 0
@@ -770,16 +783,34 @@ private struct TranscriptScroll: View {
                 model.stuck = new.distance < 80
                 return
             }
-            if model.stuck && new.distance > 1 && (new.content != old.content || new.visible != old.visible) {
+            if !model.stuck || (new.content == old.content && new.visible == old.visible) {
+                return
+            }
+            if let id = model.held {
+                position.scrollTo(id: id, anchor: .top)
+            } else if new.distance > 1 {
                 position.scrollTo(edge: .bottom)
             }
         }
         .onScrollPhaseChange { _, phase in
             scrolling = phase.isScrolling
+            if phase == .interacting {
+                model.release()
+            }
             if !scrolling {
                 model.prependOlder()
             }
         }
+        .onChange(of: model.held) { _, id in
+            if !model.stuck || scrolling {
+                return
+            }
+            if let id {
+                position.scrollTo(id: id, anchor: .top)
+            } else {
+                position.scrollTo(edge: .bottom)
+            }
+        }
         .onChange(of: model.older == nil) {
             if !scrolling {
                 model.prependOlder()
@@ -789,6 +820,7 @@ private struct TranscriptScroll: View {
             guard let new, new > old ?? 0 else {
                 return
             }
+            model.release()
             model.stuck = true
             position.scrollTo(edge: .bottom)
         }