Author the agent guide content

The v5 guide prose, verified two ways. A scripted walkthrough gave a
fresh agent nothing but the guide and a demo board: it created a card
(fresh lowercase UUID, correct bottom rank), moved one to a lane top
with modified and modified-by re-stamped, deleted one into .trash/,
attached a file into attachments/, picked `fern` off the palette table,
and quoted a colon title — and the resulting board loads through
BoardLoader with zero warnings. The walkthrough's one finding is fixed:
the trash-arrival rule now reads formulaically ("smallest order minus
1024") instead of the spatially ambiguous "below the smallest order".

Content drift-guards join the suite: every palette name the app resolves
must appear in the guide (a Palette rename now fails a test instead of
teaching agents dead colors), the rewrite's conventions are present by
name (.trash/, attachments/, modified-by, CLAUDE.user.md, the
stage-only-your-own-paths rule), and the pathfinder's retired vocabulary
(media/, tombstones) cannot resurface — the only deleted: mention is the
warning never to write it.

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

Kanban/Storage/AgentGuide.swift

@@ -335,9 +335,9 @@ enum AgentGuide {
       keys you don't recognize and don't reformat content you didn't change.
     - **Delete a card = move it into `<board>/.trash/`**: `mv <lane>/<card-uuid>
       <board>/.trash/` (create `.trash/` if missing). Arrivals go on top: set
-      the card's `order` below the smallest `order` already in `.trash/` (empty
-      trash: any number), and update `modified`. Restore is the same move in
-      reverse — into a lane, with a fresh `order`.
+      the card's `order` to the smallest `order` already in `.trash/` minus
+      1024 (empty trash: any number), and update `modified`. Restore is the
+      same move in reverse — into a lane, with a fresh `order`.
     - Never write a `deleted:` key — that convention is retired; the app
       migrates any it finds.
     - Remove a folder outright (`rm -r`) only when you mean permanent,