Registry view with element dialog; Elements and Connectors panels under diagrams

- .archify-registry opens in a new read-only custom editor (archify.registry,
  default): the file's elements as cards; click one for a dialog with its
  description, the defining line (opens the YAML) and the diagrams that use
  it (open on click); Show Source and Open Model work from the view
- the same dialog opens from the registry cards on the model page
- Archify's node index is titled Elements; a Connectors panel built from the
  SVG edges lists from → to with the label, highlights on hover and keeps the
  highlight on click; side by side in the bottom rail
- integration test for the registry view; docs and changelog

src/extension.ts

@@ -12,6 +12,7 @@ import { DiagnosticsController } from './language/diagnostics';
 import { log } from './util/log';
 import { HtmlViewerProvider } from './views/htmlViewer';
 import { DiagramViewManager } from './views/diagramView';
+import { RegistryViewProvider } from './views/registryView';
 
 export function activate(context: vscode.ExtensionContext): void {
   const models = new ModelService();
@@ -19,6 +20,7 @@ export function activate(context: vscode.ExtensionContext): void {
     extension: context,
     views: new DiagramViewManager(context, models),
     htmlViewer: new HtmlViewerProvider(context.extensionUri),
+    registry: new RegistryViewProvider(models),
     models,
   };
   const refs = new RefLanguage(models);
@@ -26,6 +28,7 @@ export function activate(context: vscode.ExtensionContext): void {
     models,
     ctx.views,
     ctx.htmlViewer,
+    ctx.registry,
     new DiagnosticsController(context, models),
     log(),
     vscode.languages.registerCompletionItemProvider(BRAND_COMPLETION_SELECTOR, new BrandCompletionProvider(context.extensionPath), ' ', '"'),