Wire Finder open as a standard document open

application(_:open:) forwards every Finder-delivered URL to
AppModel.openBoard(at:) — the exact path welcome and File > Open use, so
a Finder open gets the same registry record-before-load, recents stamp,
already-open-focuses-its-window dedup, and row-level failure surfacing
on welcome (DESIGN/02 > Launch). A cold Finder launch can arrive before
any scene has captured the window opener; openBoard now buffers such
URLs and captureWindowActions replays them once opening is possible.

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

Kanban/App/AppDelegate.swift

@@ -34,6 +34,31 @@ final class AppDelegate: NSObject, NSApplicationDelegate {
         return false
     }
 
+    /// Double-clicking a `.kanban` folder in Finder, or `open -a` — "opening a board from Finder is a
+    /// standard document open" (02-architecture.md § Launch and window lifecycle). Every URL is
+    /// forwarded to `AppModel.openBoard(at:)`, the exact entry point welcome and File ▸ Open… already
+    /// call (`AppModel.presentOpenPanel()`), so a Finder open gets the identical registry record,
+    /// board window, and recents stamp, and a board that is already open focuses its window rather
+    /// than opening a second one — `openBoard` starts its own security-scoped access on the URL, the
+    /// same as the open panel's, so nothing needs stashing here first.
+    ///
+    /// **Not pre-validated.** Info.plist's `CFBundleDocumentTypes` declares the UTI, so macOS should
+    /// never route anything but a `.kanban` folder here — but if it did, or the folder has since gone
+    /// missing, `openBoard`'s fail-fast load surfaces the failure row-level on welcome, uniform with
+    /// every other open failure. A second vocabulary for "not a board" here would just be a worse copy
+    /// of the one that already exists.
+    ///
+    /// **Can fire before any scene has appeared** — a cold launch (the app was not already running)
+    /// delivers this ahead of the first window's `onAppear`, which is where `windowOpener` is normally
+    /// captured (`CaptureOpenWindow`). `openBoard` buffers a URL that arrives that early and replays
+    /// it once the action exists, so this method does not have to reason about launch ordering itself.
+    func application(_ application: NSApplication, open urls: [URL]) {
+        guard let appModel else { return }
+        for url in urls {
+            appModel.openBoard(at: url)
+        }
+    }
+
     /// Quit runs the close flush for **every** open board before the app goes away.
     ///
     /// The same `CloseFlushCoordinator` sequence as a user close, once per board, in the same fixed