The empty provider was never load-bearing — the dragless layer frees the rubber band

Measured on real events 2026-08-07, correcting the 2026-08-06 hosted
finding: a bare count-1 tap on LaneView's empty-space layer fires in
~1-3 ms with no drag source at all — the hold that made the empty
.onDrag look necessary was the sterile NSApp.postEvent stream
over-disambiguating. And the provider was actively harmful: even an
empty drag source claims the mouse-drag at threshold, starving the
marquee's simultaneous DragGesture after one sample — the band froze
and the mouseUp never arrived. The layer goes dragless; drags from
empty space belong wholly to MarqueeControl. PointerClick's and the
layer's comments retell the corrected story. Alongside: openCard is
typed @MainActor throughout, which makes the closure Sendable and
lets CardFaceRole carry it under CardFaceView's nonisolated ==.

Claude-Session: https://claude.ai/code/session_014PtZdPwqZuqEDLc6wZMtEy

KanbanTests/BoardRenderPerformanceTests.swift

@@ -100,7 +100,7 @@ private struct ZoomedBoard: View {
     let store: BoardStore
     let window: @MainActor () -> NSWindow?
     let confirmations: TrashConfirmations
-    let openCard: (ItemID) -> Void
+    let openCard: @MainActor (ItemID) -> Void
     let search: BoardSearchPresentation
 
     @Environment(AppModel.self) private var appModel

KanbanTests/PointerLatencyTests.swift

@@ -71,7 +71,7 @@ private struct ZoomedBoard: View {
     let store: BoardStore
     let window: @MainActor () -> NSWindow?
     let confirmations: TrashConfirmations
-    let openCard: (ItemID) -> Void
+    let openCard: @MainActor (ItemID) -> Void
     let search: BoardSearchPresentation
 
     @Environment(AppModel.self) private var appModel

KanbanTests/ViewEquatableTests.swift

@@ -69,7 +69,7 @@ private func makeLane(
     slotWidth: CGFloat = 260,
     drops: BoardDropContext,
     marquee: MarqueeControl,
-    openCard: @escaping (ItemID) -> Void = { _ in }
+    openCard: @escaping @MainActor (ItemID) -> Void = { _ in }
 ) -> LaneView {
     LaneView(
         store: store,