Drop generated cards; registry descriptions become Elements tooltips

- resolveRefs no longer adds cards to a diagram; it returns node id →
  description, which the page sets as the tooltip of the matching row in
  Archify's Elements panel
- hand-written cards pass through unchanged; docs and changelog

src/model/prepare.ts

@@ -16,6 +16,8 @@ export interface PreparedDiagram {
   problems: ModelProblem[];
   /** Node id → diagram path relative to the model root. */
   links: Map<string, string>;
+  /** Node id → registry description. */
+  descriptions: Map<string, string>;
 }
 
 /**
@@ -33,5 +35,5 @@ export async function prepareDiagram(models: ModelService, uri: vscode.Uri, text
   const prepared: DiagramSource = changed
     ? { ...source, diagram: resolved.diagram, json: JSON.stringify(resolved.diagram, null, 2) }
     : source;
-  return { source: prepared, root: found?.root, registry: found?.registry, problems: resolved.problems, links: resolved.links };
+  return { source: prepared, root: found?.root, registry: found?.registry, problems: resolved.problems, links: resolved.links, descriptions: resolved.descriptions };
 }