Rows learn to be carried — long-press reorder for lanes and cards, manual mode only

An onMove on both lists, live only while the sort picker says Manual:
the drag mints a midpoint rank between its landing neighbours through
BoardWriter.moveItem's same-parent reorder path, and when a gap is
exhausted the whole container renumbers to a fresh 1024 ladder in one
perform bracket. Neither path stamps modified, so a reorder never
disturbs the Recent sort. UI suite 4/4 in the simulator.

Claude-Session: https://claude.ai/code/session_01SR4XGjmBE16ZUYWpfFHXwY

KanbanMobile/Screens/BoardScreen.swift

@@ -7,7 +7,9 @@ import SwiftUI
 /// write from anywhere in the stack (a lane created, a card moved) reaches this screen the moment
 /// the session's reload lands. A segmented control in the toolbar lets the list be sorted by
 /// name or by most recent change, on top of the board's own manual arrangement, remembered across
-/// launches.
+/// launches. Long-pressing a row drags it to a new position while `.manual` is selected — under
+/// `.name`/`.recent` the gesture is inert, since dragging a re-sorted list would reorder lanes the
+/// user is not looking at in rank order.
 struct BoardScreen: View {
     let boardRoot: URL
 
@@ -151,10 +153,68 @@ struct BoardScreen: View {
                         LaneSummaryRow(lane: lane)
                     }
                 }
+                // `nil` under `.name`/`.recent` disables the drag outright — `onMove` accepts an
+                // optional closure, so the gate lives here rather than in a branch of the `ForEach`.
+                .onMove(perform: sortOrder.wrappedValue == .manual ? { moveRows(from: $0, to: $1) } : nil)
             }
         }
         .refreshable { session.reload() }
     }
+
+    /// Commits a lane drag's release, gated to `.manual` by the `onMove` call site above — reordering
+    /// a `.name`/`.recent` re-sort would rewrite ranks for rows the user isn't seeing in rank order.
+    ///
+    /// `manualOrder` is `snapshot.lanes` with the drag already applied locally (`Array.move`), so the
+    /// dragged lane's post-drag index is both the row SwiftUI just drew and the position
+    /// `Ranks.insertionRank` mints a rank against — the same index convention `BoardStore.moveLane`
+    /// uses on the Mac. The happy path asks for the midpoint between the two neighbours the lane
+    /// lands between; on the rare board where that gap is already exhausted
+    /// (01-storage-format.md § Ordering), there is no `HealScheduler` to reach for — that engine
+    /// lives in `Kanban/LiveStore`, which this target does not compile — so the fallback renumbers
+    /// every lane to a fresh whole-multiple-of-1024 ladder in `manualOrder`'s own order, one
+    /// `BoardWriter.moveItem` reorder call per lane inside the same `session.perform` bracket. Both
+    /// paths are same-parent reorders, so neither stamps `modified` (the reorders-don't-stamp rule).
+    private func moveRows(from source: IndexSet, to destination: Int) {
+        guard let sourceIndex = source.first,
+              let snapshot = session.snapshot,
+              snapshot.lanes.indices.contains(sourceIndex)
+        else { return }
+
+        var manualOrder = snapshot.lanes
+        let moved = manualOrder[sourceIndex]
+        manualOrder.move(fromOffsets: IndexSet(integer: sourceIndex), toOffset: destination)
+        guard let landingIndex = manualOrder.firstIndex(where: { $0.id == moved.id }) else { return }
+
+        let siblingOrders = manualOrder.filter { $0.id != moved.id }.map(\.order)
+        // A `let` copy — the mutating `Array.move` above needs `manualOrder` as a `var`, but a
+        // `@Sendable` closure cannot capture a mutable var, and the fallback loop below needs the
+        // finished (post-move) arrangement, not the pre-move one.
+        let finalOrder = manualOrder
+
+        Task {
+            await session.perform { (root: URL) throws(BoardWriteError) -> MoveResult in
+                if let rank = Ranks.insertionRank(amongVisible: siblingOrders, at: landingIndex) {
+                    return try BoardWriter.moveItem(
+                        at: root.appendingPathComponent(moved.id.rawValue, isDirectory: true),
+                        toParent: root,
+                        sourceBoardRoot: root,
+                        destinationBoardRoot: root,
+                        order: rank
+                    )
+                }
+                for (lane, freshRank) in zip(finalOrder, Ranks.renumbered(count: finalOrder.count)) {
+                    _ = try BoardWriter.moveItem(
+                        at: root.appendingPathComponent(lane.id.rawValue, isDirectory: true),
+                        toParent: root,
+                        sourceBoardRoot: root,
+                        destinationBoardRoot: root,
+                        order: freshRank
+                    )
+                }
+                return MoveResult(id: moved.id, reminted: [])
+            }
+        }
+    }
 }
 
 /// One lane row: its icon when it has one, title, and its card count.