A picture off the pasteboard becomes a card's file, its hero, or the board's backdrop

⌘V grows an image-data branch, below the app's own clipboard format and refused
outright while a file URL is on the pasteboard: a screenshot or a browser's Copy
Image lands as "Pasted Image.png" in the anchor card's attachments/, through the
very import path Finder file drops and ⇧⌘A take — one bracket, one Finder-style
collision ladder, one set of banners, and the same silence a drop's arrival has.
A card window's ⌘V pastes onto its own card; a focused text field still wins the
selector natively. A file-shaped flavor travels byte for byte, PNG preferred when
several are offered; TIFF and BMP are re-encoded to PNG, being interchange
encodings rather than files anyone wants in a folder.

The hero key gets the setter it was born owing: "Set as Hero" on any image row of
the attachment list, "Remove Hero" on the row that holds it, with menu-bar twins
so the context entry is nobody's only home. It writes as a restyle — one key, one
bracket, one invertible step on the window's own stack — and replaces rather than
refusing, because a card has one hero and the row that has it says Remove instead.

Edit ▸ Paste as Board Background is the same payload's other destination, taking
the existing background.image convention at its word: the picture into the board
folder as "Pasted Background.png", the colour subkey untouched, the generator's
overwrite-our-own-name rule inherited and its echo memo taught to tell the two
producers apart.

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

Kanban/App/CardWindowHost.swift

@@ -474,6 +474,23 @@ struct CardWindowHost: View {
             .onChange(of: placement.card.attachments, initial: true) { _, names in
                 attachments.names = names
             }
+            // **The hero is the snapshot's too**, and republished the same way, so the row that
+            // offers "Remove Hero" is the row the card face is actually banding from (05 ▸
+            // Attachments; 03-board-ui.md § Card face ▸ Hero image). A malformed key reads as no
+            // hero, which is exactly what the face draws.
+            .onChange(of: placement.card.hero.value, initial: true) { _, hero in
+                attachments.hero = hero
+            }
+            // **⌘V in this window pastes a picture onto this card** (04-interactions.md ▸ Clipboard's
+            // image-data branch). Here rather than inside `CardWindowView` because the availability
+            // is the clipboard's observable reading and this is where a store, a card id and the
+            // app-wide clipboard are all in scope at once — the same join `configureAttachments`
+            // makes for the other two writes.
+            .cardWindowImagePaste(
+                store: store,
+                cardID: placement.card.id,
+                clipboard: appModel.clipboard
+            )
             .onChange(of: Self.cardFolder(root: store.rootURL, placement: placement), initial: true) { _, folder in
                 // Re-derived from the store's *current* root, `cardFolder`'s rule: a mid-session
                 // folder rename moves the board, and rows resolving against where it used to be
@@ -693,7 +710,7 @@ struct CardWindowHost: View {
         session.rawSourceIsActive = { [rawSource] in rawSource.isActive }
         session.rawSourceApply = { [rawSource] in rawSource.applyAndLeave() }
         session.rawSourceCancel = { [rawSource] in rawSource.cancel() }
-        Self.configureAttachments(attachments, store: store, cardID: cardID)
+        Self.configureAttachments(attachments, store: store, cardID: cardID, undo: session.undo)
         Self.configureComments(session.comments, store: store, cardID: cardID, on: session.undo)
     }
 
@@ -811,13 +828,24 @@ struct CardWindowHost: View {
     /// `static`, and taking every collaborator as a parameter, for `configureRawSource`'s reason:
     /// the target resolution is invisible in a running window until it is wrong, and this shape is
     /// what lets a test drive the real wiring rather than a re-typed copy of it.
-    static func configureAttachments(_ attachments: CardAttachments, store: BoardStore, cardID: ItemID) {
+    static func configureAttachments(
+        _ attachments: CardAttachments,
+        store: BoardStore,
+        cardID: ItemID,
+        undo: CardWindowUndo
+    ) {
         attachments.importFiles = { [weak store] urls in
             store?.importAttachments(urls, toCard: cardID)
         }
         attachments.removeFile = { [weak store] name in
             store?.removeAttachment(named: name, fromCard: cardID)
         }
+        // **The window's own stack**, like every other gesture issued in this window
+        // (13-native-undo.md ▸ Rules ▸ two levels): Set as Hero is a restyle, and a restyle made here
+        // folds into this session's close step rather than landing on the board's.
+        attachments.setHeroFile = { [weak store] name in
+            store?.setHero(name, onCard: cardID, on: undo)
+        }
     }
 
     /// Points the raw-source outlet at its card — the outlet's three seams (05-card-window.md ▸ Raw