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

Kanban/UI/Board/BoardView.swift

@@ -67,7 +67,7 @@ struct BoardView: View {
     /// Opens a card's window — ⌘↩'s second half (04-interactions.md ▸ Grammar). A closure from
     /// `BoardWindowHost` rather than an `openWindow` call here, because building a `CardWindowRef`
     /// needs the board's own window ref, which is the host's identity and not the board's.
-    let openCard: (ItemID) -> Void
+    let openCard: @MainActor (ItemID) -> Void
 
     /// The toolbar search field's handle (`BoardSearchPresentation`), threaded down so the strip can
     /// fill in `focusBoard` — Escape's "in an empty field it returns focus to the board" needs the