Comments, phase 2 — the pane, the composer, and the inline session

The card window recomposes into three componentized panes (body,
comments, attributes) with two mounts — beside or body-over-comments
at ~3:2 — behind View ▸ Comments Beside Body. View ▸ Show Comments is
one persisted app-wide bit, no content-derived auto-show; File ▸ Add
Comment flips it on and focuses the composer. The thread renders
author lines, edited markers, card-subset Markdown bodies, and
read-only Quick Look chips under a count header with the sort-
direction control. The composer edits comments/.draft/ on the slow
cadence (blur, close, quit, ~30s interval), Escape only moves focus,
⌘↩ posts. Inline edit is a body-edit session in miniature: 700ms
debounce, Save/⌘↩ commits, Cancel and Escape revert to session-start
bytes, close flushes. File drops within either authoring surface
carve out of the window-wide card default into that surface's
attachments/; paperclips cover the no-drag path. Close flush runs
inline flush, then draft save, then the comments/.trash purge;
open sweeps crash residue.

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

Kanban/App/AppModel.swift

@@ -60,6 +60,53 @@ public enum AppPreferences {
         UserDefaults.standard.set(NSStringFromSize(size), forKey: lastCardWindowSizeKey)
     }
 
+    // MARK: The comments pane's three bits
+
+    /// **View ▸ Show Comments** — "a checkmark toggle à la Show Trash, and its choice is **app-wide
+    /// and persisted across restarts**" (05-card-window.md ▸ The comments column, re-ruled
+    /// 2026-07-29; 11-command-nexus.md).
+    ///
+    /// **One bit, and no content-derived auto-show**: checked, every card window carries the pane —
+    /// a comment-less card shows the empty thread and the composer, because the invitation is the
+    /// point; unchecked, threads and drafts are out of sight until the user says otherwise. The
+    /// checkmark reads exactly this value, so the menu never lies, and deleting the last comment
+    /// never closes the pane because nothing but this bit does.
+    ///
+    /// **Default on.** 05 does not spell a default, and the two candidate readings pull in opposite
+    /// directions — the Show Trash bargain (a secondary surface, default off) against "the invitation
+    /// is the point" (a pane whose empty state is its whole argument). The invitation wins: a
+    /// comments feature nobody sees until they find a View-menu row is a feature that is not there,
+    /// and the user who does not want it turns it off once, forever, which is what the persistence is
+    /// for.
+    public static let showCommentsKey = "showComments"
+
+    public static var showComments: Bool {
+        UserDefaults.standard.object(forKey: showCommentsKey) as? Bool ?? true
+    }
+
+    /// **View ▸ Comments Beside Body** — "checked = side-by-side (default), unchecked = body over
+    /// comments; app-wide, persisted" (11-command-nexus.md; 05 ▸ Composition).
+    ///
+    /// Default **on**, which 05 does state: "side-by-side is the default".
+    public static let commentsBesideBodyKey = "commentsBesideBody"
+
+    public static var commentsBesideBody: Bool {
+        UserDefaults.standard.object(forKey: commentsBesideBodyKey) as? Bool ?? true
+    }
+
+    /// The comments header's **sort-direction control** — "chronological ascending by default,
+    /// flippable to newest-first (app-wide, persisted)" (05 ▸ The comments column; 11 files it under
+    /// Configuration controls).
+    ///
+    /// Stored as "newest first" rather than as a direction so the default is `false` and the plain
+    /// `bool(forKey:)` reading is the right one — the one preference here that does not need to tell
+    /// "off" from "never set".
+    public static let commentsNewestFirstKey = "commentsNewestFirst"
+
+    public static var commentsNewestFirst: Bool {
+        UserDefaults.standard.bool(forKey: commentsNewestFirstKey)
+    }
+
     /// The quick-style row's recently-used backgrounds — an array of palette names / hex strings,
     /// most-recent-first (03-board-ui.md § Styling ▸ Controls: "Recents are app-wide and persist
     /// app-side (user preference, never board data)"; 11-command-nexus.md files it under the