The clear title bar is said in SwiftUI — a configuration pass stops painting the bar back over the board's picture

`titlebarAppearsTransparent` is not the app's to hold on a scene window: it is
the AppKit face of the tree's resolved `toolbarBackgroundVisibility`, and
SwiftUI writes it on every pass that re-applies a window's configuration. The
board stated nothing, so `.automatic` resolved and each pass put `false` back
over what `HostedWindowController` had set out of band — correct on open,
because the walk lands after the pass that follows window creation, and opaque
at the next one, with nothing to re-assert it since the board's own reading had
not changed. The board now declares the posture where SwiftUI will keep
asserting it; the AppKit write stays as the same value one turn earlier.

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

Kanban/App/WindowAccessor.swift

@@ -285,6 +285,18 @@ final class HostedWindowController: NSObject, NSWindowDelegate {
     /// what stops the title bar from painting its own material over it. Either alone is a visible
     /// half-state — an opaque bar over the board, or a board that stops at a bar that no longer
     /// draws.
+    ///
+    /// **The second knob does not stay written, and this is not the place that keeps it.** On a
+    /// SwiftUI scene window `titlebarAppearsTransparent` is SwiftUI's: it is the AppKit face of the
+    /// view tree's resolved `toolbarBackgroundVisibility(for: .windowToolbar)`, and SwiftUI writes
+    /// the resolved value — changed or not — on every pass in which it re-applies a window's
+    /// configuration. A tree that states nothing resolves `.automatic`, so each of those passes put
+    /// `false` back over what this method had set, and the board's title bar went opaque some time
+    /// after the board opened rather than at once. So the board *also* says it in SwiftUI
+    /// (`BoardWindowHost`, which owns the reasoning), and this write is what makes the posture true
+    /// for the turn in which the board's `background:` first reads, not what makes it last.
+    ///
+    /// The `fullSizeContentView` half has no such second owner and survives on its own.
     private func applyTitlebarExtensionIfPossible() {
         guard let window, let extendsUnderTitlebar else { return }
         window.titlebarAppearsTransparent = extendsUnderTitlebar