Architecture decisions: files, diagram references, views and panels

- *.archify-decision files: id (unique, words), title, status, date,
  elements, diagrams, supersedes, and prose; parsed, merged and link-checked
  in the model index; diagnostics on the file
- diagrams point at decisions with decisions: [...] on the diagram, nodes
  and edges; stripped before Archify, unknown ids reported, completion,
  hover and go-to-definition for the ids and for elements/diagrams/
  supersedes in decision files
- Decisions panel on the main.archify page; Decisions rail panel under a
  diagram (hover lights up the node or connection); decisions on element
  cards and in the element dialog; decision view for the file, with a
  lost-model note outside a model
- Archify | New Decision… command and template; editor schemas; the three
  New Model examples carry decisions; docs, changelog, 0.8.0

src/views/registryView.ts

@@ -7,7 +7,7 @@ import { readText } from '../util/files';
 import { log } from '../util/log';
 import { handleWebviewMessage, WebviewMessage } from '../webview/messages';
 import { makeNonce, registryPage } from '../webview/page';
-import { DIAGRAM_EDITOR_VIEW_TYPE, REGISTRY_VIEW_TYPE } from './viewTypes';
+import { DECISION_VIEW_TYPE, DIAGRAM_EDITOR_VIEW_TYPE, REGISTRY_VIEW_TYPE } from './viewTypes';
 
 export { REGISTRY_VIEW_TYPE };
 
@@ -32,6 +32,7 @@ class RegistryView implements vscode.Disposable {
       panel.webview.onDidReceiveMessage((message: WebviewMessage) => {
         if (message.type === 'openDiagram') return void this.openInModel(message.path, DIAGRAM_EDITOR_VIEW_TYPE);
         if (message.type === 'openRegistry') return void this.openRegistryLine(message.file, message.line);
+        if (message.type === 'openDecision') return void this.openInModel(message.file, DECISION_VIEW_TYPE);
         void handleWebviewMessage(message, this.uri, this.panel);
       }),
     );