Build the template chooser and Save as Template

The chooser completes its three tiers: bundled by template order, then
keyed user templates, then keyless boards by display name — and a
malformed user template still lists, by folder name with the loader's
own sentence on the row, never failing its neighbours. The store is
re-scanned on every presentation and on app activation, the Reveal
round trip made honest without watching a folder 09 deliberately
leaves unwatched; Reveal lives in the chooser's header and mints the
store on first press. Save as Template repeats Duplicate's sequence —
progress row with Cancel, flush, detached cancellable copy — through
the engine: mint the store, read the next user order before the copy
can count itself, Finder-ladder the name, copy excluding .git and
.trash/, then stamp the whole template: mapping on the landed copy
through updateIndex, with no bracket because the copy lives outside
every watched board. Folder attributes deliberately don't carry — the
one lock the command stays live under is the read-only-DMG one, and
carrying its mode bits would mint a read-only template in the user's
own store; the command gates instead on the real hazard, unsaved card
content. A signpost names the template only when the ladder renamed
it. One name ladder now serves Duplicate and the store.

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

Kanban/App/BoardDuplicator.swift

@@ -100,18 +100,40 @@ enum BoardDuplicator {
     /// the sandbox will not let us write is usually one we cannot list either, so the ladder simply
     /// finds no collision and suggests `"Board copy"` — the right pre-fill, arrived at honestly.
     static func copyDestination(for rootURL: URL) -> URL {
-        let parent = rootURL.deletingLastPathComponent()
-        let base = rootURL.deletingPathExtension().lastPathComponent
-        let ext = rootURL.pathExtension
+        uncollidedURL(
+            named: "\(rootURL.deletingPathExtension().lastPathComponent) copy",
+            extension: rootURL.pathExtension,
+            in: rootURL.deletingLastPathComponent()
+        )
+    }
 
+    /// **Finder's counting ladder, in one place**: `name`, then `name 2`, `name 3`, … counting up
+    /// from 2 against what is on disk at decision time, one collision at a time.
+    ///
+    /// Shared rather than spelled twice, because two flows want the same ladder from different
+    /// starting names: Duplicate seeds it with `"Board copy"` (above), and Save as Template seeds it
+    /// with the board's own name — 09-templates.md ▸ Save as Template's "**Store collisions
+    /// auto-rename, Finder-style** (`Board.kanban` → `Board 2.kanban`) — the 01 import precedent:
+    /// saving never overwrites an existing template and never refuses". One ladder, two seeds, so
+    /// the two can never disagree about what "Finder-style" means.
+    ///
+    /// The extension rides on the end (`Board copy.kanban`) and an extension-less board folder
+    /// simply has none to carry — both are shapes a board is allowed to be (01-storage-format.md
+    /// § Document packaging).
+    ///
+    /// `fileExists` is the one test, and it is true for a file as much as a folder: anything already
+    /// wearing the name blocks it, which is what keeps either flow from overwriting something. It is
+    /// a decision-time answer, not a reservation — the caller still creates the folder itself and
+    /// still fails rather than clobbers if the name was taken in between.
+    static func uncollidedURL(named base: String, extension ext: String, in parent: URL) -> URL {
         func candidate(_ name: String) -> URL {
             parent.appendingPathComponent(ext.isEmpty ? name : "\(name).\(ext)", isDirectory: true)
         }
 
-        var name = "\(base) copy"
+        var name = base
         var counter = 2
         while FileManager.default.fileExists(atPath: candidate(name).path) {
-            name = "\(base) copy \(counter)"
+            name = "\(base) \(counter)"
             counter += 1
         }
         return candidate(name)