File ▸ Share… stages a board as a zip and hands it to the system share sheet

Duplicate's own posture — a faithful copy, `.git` the sole exclusion, attachments/comments/trash
carried verbatim — staged to a temp directory (BoardShareStager, ditto-zipped via
DittoZipArchiver) and presented through NSSharingServicePicker (BoardSharePresentation), anchored
to the board window's toolbar or its center. Follows Duplicate/Save as Template's flush-then-
cancellable-copy sequence under the banner's in-progress row (ShareBoardCommand, AppCommands.swift),
menu-validated on focus alone rather than the read-only lock (a share is a read, Print's own
posture) with the one carve-out an open inline title editor still needs. WriteOperation gains
.shareBoard for the banner vocabulary; 11-command-nexus.md's File menu table gains the row.

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

Kanban/Storage/BoardWriter.swift

@@ -3010,6 +3010,14 @@ public enum WriteOperation: Sendable, Equatable, CustomStringConvertible {
     /// `title` is the board's display name.
     case saveAsTemplate(title: String?)
 
+    /// File ▸ Share… — the whole board staged into a `.zip` for `NSSharingServicePicker`
+    /// (design ruling 2026-08-09, card 72691b11; `BoardShareStager`). Its own case beside
+    /// `.duplicateBoard` and `.saveAsTemplate`, on both their reasoning: a third command copies a
+    /// board wholesale for a third reason, and a banner saying the app could not "duplicate" or
+    /// "save as template" a board nobody asked to duplicate or template would name gestures that
+    /// never happened. `title` is the board's display name.
+    case shareBoard(title: String?)
+
     case importAttachment(filename: String)
     case listAttachments
 
@@ -3246,6 +3254,7 @@ public enum WriteOperation: Sendable, Equatable, CustomStringConvertible {
         case .rename: .rename(title: title)
         case .duplicateBoard: .duplicateBoard(title: title)
         case .saveAsTemplate: .saveAsTemplate(title: title)
+        case .shareBoard: .shareBoard(title: title)
         case .toggleTask: .toggleTask(title: title)
         case .editBody: .editBody(title: title)
         case .rawSource: .rawSource(title: title)
@@ -3289,7 +3298,7 @@ public enum WriteOperation: Sendable, Equatable, CustomStringConvertible {
         // reading to be about — and `.deleteComment`'s move into `comments/.trash/` stamps for the
         // plain container reason its board-level twin does.
         case .createBoard, .createLane, .createCard, .move, .copy, .delete, .purge, .migrateTombstone,
-             .style, .resize, .collapse, .expand, .rename, .duplicateBoard, .saveAsTemplate, .paste,
+             .style, .resize, .collapse, .expand, .rename, .duplicateBoard, .saveAsTemplate, .shareBoard, .paste,
              .importAttachment,
              .listAttachments, .removeAttachment, .relocateLooseFile, .agentGuide, .seedGitignore,
              .mintBoardIndex, .stampSchema, .setBoardBackground,
@@ -3326,6 +3335,7 @@ public enum WriteOperation: Sendable, Equatable, CustomStringConvertible {
         case let .rename(title): Self.phrase("rename", title)
         case let .duplicateBoard(title): Self.phrase("duplicate board", title)
         case let .saveAsTemplate(title): Self.phrase("save as template", title)
+        case let .shareBoard(title): Self.phrase("share board", title)
         case let .importAttachment(filename): "import attachment '\(filename)'"
         case .listAttachments: "list attachments"
         case let .removeAttachment(filename): "move attachment '\(filename)' to the Trash"