Registry as Archify cards on the model page; cards under model diagrams from registry descriptions

- model page: registry elements are rendered as Archify info cards (type
  colour dot, label, id · type, description, used-in chips that open the
  diagram), replacing the table
- resolveRefs: a diagram without cards of its own gets one card per drawn
  shared element that has a description, so the registry text shows under
  every model diagram as it does on hand-written diagrams
- unit tests for generated cards, own cards winning and no cards without
  refs; docs and changelog

src/model/format.ts

@@ -55,6 +55,42 @@ export interface Registry {
   problems: ModelProblem[];
 }
 
+/** Archify card dot colour for a component type (the colours Archify gives the nodes). */
+const DOT_BY_TYPE: Record<string, string> = {
+  frontend: 'cyan',
+  backend: 'emerald',
+  database: 'violet',
+  cloud: 'amber',
+  security: 'rose',
+  messagebus: 'orange',
+  external: 'slate',
+};
+
+export function dotForType(type?: string): string {
+  return DOT_BY_TYPE[type ?? ''] ?? 'slate';
+}
+
+export interface Card {
+  dot: string;
+  title: string;
+  items: string[];
+}
+
+/**
+ * Archify info cards for registry elements: one per element that has a
+ * description, titled by its label. What a diagram gets below itself when
+ * it draws shared elements and defines no cards of its own.
+ */
+export function cardsFromElements(elements: Iterable<RegistryElement>): Card[] {
+  const cards: Card[] = [];
+  for (const element of elements) {
+    if (!element.description) continue;
+    const items = [element.description.trim()];
+    cards.push({ dot: dotForType(element.type), title: element.label ?? element.id, items });
+  }
+  return cards;
+}
+
 export function isMainFile(fileName: string): boolean {
   return (fileName.split(/[\\/]/).pop() ?? '') === MAIN_FILE;
 }
@@ -172,6 +208,8 @@ export interface ResolveOptions {
  * Expands `ref` components from the registry and strips what Archify does
  * not know. Component order and indexes are kept, so Archify's diagnostics
  * (JSON pointers) still point at the right component in the source file.
+ * A diagram without `cards` of its own gets cards from the descriptions of
+ * the shared elements it draws, so the registry text shows under the diagram.
  */
 export function resolveRefs(doc: unknown, options: ResolveOptions): ResolvedDiagram {
   const problems: ModelProblem[] = [];
@@ -229,6 +267,13 @@ export function resolveRefs(doc: unknown, options: ResolveOptions): ResolvedDiag
     if (link) links.set(id, link);
     return merged;
   });
+  if (diagram.cards === undefined && refs.size) {
+    const seen = new Set<string>();
+    const elements: RegistryElement[] = [];
+    for (const element of refs.values()) if (!seen.has(element.id)) { seen.add(element.id); elements.push(element); }
+    const cards = cardsFromElements(elements);
+    if (cards.length) diagram.cards = cards;
+  }
   return { diagram, problems, refs, links, used };
 }