The drag replicas cast the shadow the pickup lift already promised

DragReplicaStyle spells the pathfinder's constant ambient shadow once
(black 16%, radius 2.5, y 1.5) and all three replica faces — card,
lane, trashed lane — wear it via one modifier; the ghost fans compose
from the same faces so every copy inherits it, dimmed by its own
opacity. 03 § Motion's "pickup lift (scale + shadow)" supplies the
scale from the system session but no shadow on the preview image — the
replica is the only place it can come from. BoardMetrics.replicaPadding
was already written to keep exactly this shadow from clipping and was
simply unused until now.

Drag-perf card 24397310.

Claude-Session: https://claude.ai/code/session_01CqjXB7ASoWtbyoGod68k97

Kanban/UI/Board/DragShadow.swift

@@ -78,3 +78,23 @@ struct DragCountBadge: View {
         }
     }
 }
+
+/// The pickup lift's shadow figures — 03-board-ui.md § Motion's "the pickup lift (scale + shadow as
+/// it detaches from the card)": the system drag session supplies the scale and the tracking, but
+/// paints no shadow onto its preview image, so the shadow can only come from the replica view
+/// itself. Values are the pathfinder's own constant ambient shadow, reused verbatim rather than
+/// re-derived (`~/Documents/indie/Kanban` CardView.swift:623) — its drags read subtly raised, and
+/// that read is the point.
+enum DragReplicaStyle {
+    static let shadowColor = Color.black.opacity(0.16)
+    static let shadowRadius: CGFloat = 2.5
+    static let shadowY: CGFloat = 1.5
+}
+
+extension View {
+    /// The pickup lift's shadow (`DragReplicaStyle`), for a drag replica's face — shared by the
+    /// card, lane, and trashed-lane replicas so the figures are spelled once.
+    func dragReplicaShadow() -> some View {
+        shadow(color: DragReplicaStyle.shadowColor, radius: DragReplicaStyle.shadowRadius, y: DragReplicaStyle.shadowY)
+    }
+}