The board wears a picture — background becomes a mapping, and the window chrome follows it under a thin frost

background is {color:, image:} and only a mapping at every level; the board's image paints the full window under a transparent title bar, with a thin-material frost strip keeping the chrome legible and the standard accommodations intact.

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

Kanban/LiveStore/BoardStore.swift

@@ -1931,11 +1931,16 @@ public final class BoardStore: HealHost {
         }
     }
 
+    /// Through `setStyleValue` rather than `set`/`remove` directly, which is this gesture's whole
+    /// answer to `background` being a mapping (BackgroundField.swift): the colour is written *into*
+    /// the key rather than over it, so a board carrying `background: {color: …, image: …}` comes out
+    /// of a colour change still carrying its image. `icon` takes the plain scalar path through the
+    /// same call.
     private static func apply(_ change: StyleChange, to key: String, in document: inout FrontmatterDocument) {
         switch change {
         case .keep: break
-        case let .set(value): document.set(key, to: .string(value))
-        case .remove: document.remove(key)
+        case let .set(value): document.setStyleValue(value, for: key)
+        case .remove: document.setStyleValue(nil, for: key)
         }
     }