board: a card turns over to a checklist, labels and a description

Enter on a card floats a sheet over the board: its labels, a markdown
description written in the vim editor (:w writes it to the card), and a
checklist walked with j/k, ticked with Space, grown with o. Labels take
their colour from their name. A repeating card comes back with its
checklist reopened.

Code in the editor and in rendered fences is coloured from nvim's
yorha.lua, one class per highlight group, for every language
@codemirror/language-data knows; the languages load on first use.

web/src/lib/api.ts

@@ -170,11 +170,20 @@ export interface Card {
   done_at: number | null
   /** `daily`, `weekly`, `monthly`, `yearly`, `+3d`, `+2w`, `+6m` — or none. */
   repeat: string | null
+  checklist: Task[]
+  /** Lower case, each once. */
+  labels: string[]
   position: number
   created_at: number
   updated_at: number
 }
 
+/** A step on a card's checklist. */
+export interface Task {
+  text: string
+  done: boolean
+}
+
 /** A card after a move or an edit, and the copy a repeating card it finished left in the inbox. */
 export interface Moved extends Card {
   again: Card | null
@@ -564,6 +573,9 @@ export const api = {
       node_id?: number | null
       due_at?: number | null
       repeat?: string | null
+      /** The whole checklist, as it should now read. */
+      checklist?: Task[]
+      labels?: string[]
       done?: boolean
     },
   ) => request<Moved>(`/cards/${id}`, { method: 'PUT', body: body(patch) }),