Build Edit mode with debounced, byte-honest saves

The editing surface: the same hosted TextKit-1 text view gains an
editable branch with a per-keystroke line-scanner highlighter — chosen
over a parser re-parse because a mid-typing buffer is usually invalid
Markdown and 05 wants the delimiters themselves dimmed; apply only sets
attributes, so presentation-never-transforms is structural. Saves ride
a ~700ms injectable debounce through BoardWriter.writeBody —
toggleTaskMarker's idiom widened to the body span, frontmatter bytes
untouched, refusing to write when disk already holds that body, which
enforces all three gates (untouched, reverted, echo) at the layer that
owns the bytes with one isDirty predicate above it. Mode grammar lands
whole: ⌘E toggles with a checkmark, Return in Preview enters, Escape
returns, and every flip flushes first; window close flushes through
the existing retry/save-copy/discard modal, and the dismissal flush
deliberately reaches a tombstoned card. Dirty-buffer-wins: disk always
follows the snapshot, the buffer only when clean, both surfaces render
the buffer. Undo is the editor's own session-scoped NSUndoManager;
endEditSession names the pro-m1 one-commit-per-session boundary.

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

Kanban/App/FutureCommands.swift

@@ -108,14 +108,20 @@ struct FindSteppingCommands: View {
 /// View ▸ Edit Body (⌘E) / Raw Source (⌥⌘E) / History — the card window's three view-state rows
 /// (11-command-nexus.md).
 ///
-// m6-card-window: Edit Body and Raw Source are checkmark toggles reading the window's edit-mode
-// state ("Edit Body disables while Raw Source is active" — 05-card-window.md); History is a plain
-// command that focuses the sidebar's History section and disables outright on mode `none` /
-// repo-nested boards once that section exists (05-card-window.md, 07-sync-collab.md). All three are
-// unconditionally disabled here — there is no card-window mode state anywhere yet.
+/// **Edit Body is live** (`EditBodyCommand`, beside the focused value it reads): the body column's
+/// Preview/Edit toggle, checkmark state and all. Its diff was the one `FutureCommand` promises —
+/// the title and the chord did not move, the validation and the action filled in.
+///
+// m6-raw-source: Raw Source is the same shape one card later — a checkmark toggle over a
+// window-level mode, which also adds the "Edit Body disables while Raw Source is active" clause to
+// the row above (05-card-window.md).
+//
+// m6-card-sidebar: History is a plain command that focuses the sidebar's History section, and
+// disables outright on mode `none` / repo-nested boards once that section exists (05-card-window.md,
+// 07-sync-collab.md). Both remain unconditionally disabled here — neither surface exists yet.
 struct CardViewCommands: View {
     var body: some View {
-        FutureToggleCommand(title: "Edit Body", key: "e", modifiers: .command)
+        EditBodyCommand()
         FutureToggleCommand(title: "Raw Source", key: "e", modifiers: [.option, .command])
         FutureCommand(title: "History")
     }