Fix press-and-hold mic dying instantly in private chats (#1405)

The private-chat sheet wraps its entire content — composer included — in a
high-priority swipe-right-to-leave DragGesture. A high-priority ancestor
drag preempts child gestures, so the composer mic's press-and-hold was
cancelled 3-10 ms after touch-down (observed on both iOS and macOS in field
logs), making voice notes unrecordable inside DMs while working fine in the
public timeline. Same starvation mechanism as the DM image-reveal bug
(#1402), hitting a drag instead of a tap.

The swipe-to-leave gesture now attaches to the message list only — where
users actually swipe — leaving the composer's gestures (mic hold, text
field, buttons) out of its reach.

Co-authored-by: jack <jackjackbits@users.noreply.github.com>
Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

bitchat/Views/ContentSheetViews.swift

@@ -393,6 +393,11 @@ private struct ContentPrivateChatSheetView: View {
             )
             .themedSurface()
             .frame(maxWidth: .infinity, maxHeight: .infinity)
+            // Swipe-right-to-leave lives on the message list only. On the
+            // whole sheet it preempted the composer's press-and-hold mic
+            // gesture (a high-priority ancestor drag cancels child gestures
+            // within milliseconds — same starvation as the image-reveal bug).
+            .highPriorityGesture(swipeToLeaveGesture)
 
             if !theme.usesGlassChrome {
                 Divider()
@@ -423,7 +428,9 @@ private struct ContentPrivateChatSheetView: View {
         }
         .themedSheetBackground()
         .foregroundColor(palette.primary)
-        .highPriorityGesture(
+    }
+
+    private var swipeToLeaveGesture: some Gesture {
         DragGesture(minimumDistance: 25, coordinateSpace: .local)
             .onEnded { value in
                 let horizontal = value.translation.width
@@ -434,7 +441,6 @@ private struct ContentPrivateChatSheetView: View {
                     privateConversationModel.endConversation()
                 }
             }
-        )
     }
 
     /// Persistent one-line reminder that this composer feeds a private