Build the welcome screen

The welcome window becomes the real thing: Xcode-style, hidden title
bar with background drag, branding and actions left, recents right —
rows carrying the board symbol, name, location, and the registry's
cached lane/card counts (stamped at close, never a scan at welcome
time), sorted by last opened. Launch failures surface row-level per
02: a failure joins its recents row as a warning caption, an
unresolvable bookmark renders unavailable with Forget its one
affordance, and only a failure with no row to carry it falls back to
a compact list; a board opening again heals its row. New Board
(Opt-Cmd-N) opens the Pages-style template chooser — shipped with
the single Basic template and the m9 seams marked — flowing through
the save panel into createBoard/createLane and straight into a board
window. Open Recent gains its submenu with Clear Menu (byte-identical
to forgetting every row, pinned by test), and File > Duplicate forks
the frontmost board to a Finder-style copy sibling: pending work
flushes first through the close flush's step two alone (sessions stay
open — 09's stated exception), every GUID and tombstone carries (the
whole-board carve-out from copies-remint), and the copy opens in its
own window while the original stays put. 36 new tests.

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

Kanban/App/CloseFlushCoordinator.swift

@@ -198,7 +198,13 @@ public struct CloseFlushCoordinator {
 
     /// Step 2. The store's pipeline, then the editor saves, then the pending commit — 02's order,
     /// stated once.
-    private func flushPendingWork() async {
+    ///
+    /// **Callable on its own**, which is the one place the sequence is entered part-way: File ▸
+    /// Duplicate needs pending work on disk before it copies but must leave the session standing
+    /// (09-templates.md ▸ Save as Template's stated exception — "sessions staying open"). It reaches
+    /// this step through `AppModel.flushPendingWork(for:)` rather than re-listing the three flushes,
+    /// so their order still has one definition.
+    public func flushPendingWork() async {
         await storeFlush()
         await editorFlush?()
         await committerFlush?()