Build the attachments sidebar section

The card's complete file inventory: compact QuickLook-thumbnail rows
over Card.attachments — no reference tracking, subfolders tolerated
and unsurfaced — with a quiet header add affordance and the drop hint
empty state. The whole window is the file-drop surface, Edit mode
included (the editor's drag types were already filtered; now tested),
sharing the board's folder-refusal semantics literally: FinderDrop
moved verbatim into its own file so both windows run the same
partition and loss row. Dragged text still lands at the caret and is
inert elsewhere — the window delegate accepts file payloads only.
Rows open on double-click or Return, drag out their file URL, and
Remove is a bracketed write through FileManager.trashItem — the system
Trash, never a hard delete, returning the in-Trash URL so the promise
is testable; the attachment listing is the guard, so traversal and
subfolder names refuse in one line. Keyboard-native per 05: the
section is one Tab stop, arrows walk rows by name, Space toggles the
shared QuickLook panel, Backspace removes. File > Add Attachment
(shift-cmd-A) comes alive through the same import path.

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

Kanban/App/FutureCommands.swift

@@ -52,27 +52,10 @@ struct SaveAsTemplateCommand: View {
     }
 }
 
-// MARK: - File ▸ Add Attachment…
-
-/// File ▸ Add Attachment… (⇧⌘A) — card window only (11-command-nexus.md).
-///
-// m6-card-window: the menu-bar twin of the attachments section's quiet add affordance
-// (05-card-window.md § Attachments) and of a whole-window Finder file drop. Validation will be scope
-// alone — a card window in front, the read-only lock aside — `BoardInfoCommand`'s shape for its own
-// scope-only item.
-//
-// m5-context-menus, m6-card-window: the attachment row's own context menu is a second thing this
-// milestone owes — Open, Remove (system Trash), Reveal in Finder (11-command-nexus.md ▸ Context
-// menus' Attachment row), twinning the focused section's grammar keys (Return open / ⌫ remove — 05
-// ▸ Attachments) and Reveal in Finder's attachments-focused scope, exactly the way this milestone's
-// card and lane menus twin their own grammar and menu-bar commands: no new store method, no parallel
-// implementation. There is no row view to hang a `.contextMenu` off yet, so nothing scaffolds here
-// beyond this marker.
-struct AddAttachmentCommand: View {
-    var body: some View {
-        FutureCommand(title: "Add Attachment…", key: "a", modifiers: [.shift, .command])
-    }
-}
+// File ▸ Add Attachment… (⇧⌘A) was the scaffold here and is now live, beside the focused value it
+// reads (`AddAttachmentCommand`, in `CardAttachments.swift`) — the diff this file predicts: the
+// title and the chord did not move, the validation and the action filled in. The attachment row's
+// context menu (Open / Remove / Reveal in Finder) shipped with it, on the row view that now exists.
 
 // MARK: - Edit ▸ Find Next / Find Previous