Add Archify | New Model… with three C4 examples and Open Model in the Explorer menu

- templates/models: C4 - Standard Web App, C4 - E-Shop, C4 - Event-Based
  Integration; each a complete model (main.archify, registry, context,
  containers, components) that validates
- archify.newModel: pick an example and a folder name, copy it, name the
  model after the folder, open the model page
- Explorer menu: New Model… on folders, Open Model on .archify and
  .archify-registry files; File → New File… lists New Model…
- unit test validates every example end to end; integration test runs the
  command; README, CHANGELOG, docs/model.md

test/integration/suite.ts

@@ -340,4 +340,51 @@ export async function run(): Promise<void> {
     assert.match(content, /id: new-shop/);
     assert.match(content, /name: New shop/);
   });
+
+  await check('Archify | New Model… creates a model folder from an example and opens its page', async () => {
+    const commands = vscode.extensions.getExtension(EXTENSION_ID)?.packageJSON.contributes.commands as { command: string; title: string }[];
+    assert.equal(commands.find((item) => item.command === 'archify.newModel')?.title, 'Archify | New Model…');
+    const parent = workspaceFile('.');
+    const window = vscode.window as unknown as Record<string, unknown>;
+    const originalPick = window.showQuickPick;
+    const originalInput = window.showInputBox;
+    let labels: string[] = [];
+    let existingNameMessage: unknown;
+    window.showQuickPick = async (items: readonly { label: string }[]) => {
+      labels = (await items).map((item) => item.label);
+      return (await items).find((item) => item.label === 'C4 - E-Shop');
+    };
+    window.showInputBox = async (options: vscode.InputBoxOptions) => {
+      existingNameMessage = await options.validateInput?.('new-shop');
+      return 'shop-two';
+    };
+    try {
+      await vscode.commands.executeCommand('archify.newModel', parent);
+    } finally {
+      window.showQuickPick = originalPick;
+      window.showInputBox = originalInput;
+    }
+    assert.deepEqual(labels, ['C4 - Standard Web App', 'C4 - E-Shop', 'C4 - Event-Based Integration']);
+    assert.match(String(existingNameMessage), /already exists/);
+    const folder = vscode.Uri.joinPath(parent, 'shop-two');
+    const main = vscode.Uri.joinPath(folder, 'main.archify');
+    const content = new TextDecoder().decode(await vscode.workspace.fs.readFile(main));
+    assert.match(content, /id: shop-two/);
+    assert.match(content, /name: Shop two/);
+    assert.match(content, /title: Shop two — overview/);
+    const names = (await vscode.workspace.fs.readDirectory(folder)).map(([name]) => name).sort();
+    assert.deepEqual(names, ['0100-context', '0200-containers', '0300-components', 'main.archify', 'registry']);
+    const registry = (await vscode.workspace.fs.readDirectory(vscode.Uri.joinPath(folder, 'registry'))).map(([name]) => name).sort();
+    assert.deepEqual(registry, ['containers.archify-registry', 'people.archify-registry', 'systems.archify-registry']);
+    const tab = await waitFor('model page tab', () =>
+      vscode.window.tabGroups.all.flatMap((g) => g.tabs).find((t) => t.isActive && t.input instanceof vscode.TabInputCustom && t.input.uri.toString() === main.toString()),
+    );
+    assert.ok(tab);
+    // The new model is indexed: its diagrams resolve against the copied registry.
+    const containers = await vscode.workspace.openTextDocument(vscode.Uri.joinPath(folder, '0200-containers', 'online-shop.archify'));
+    await vscode.window.showTextDocument(containers);
+    await new Promise((resolve) => setTimeout(resolve, 1500));
+    const errors = vscode.languages.getDiagnostics(containers.uri).filter((d) => d.severity === vscode.DiagnosticSeverity.Error);
+    assert.deepEqual(errors.map((d) => d.message), []);
+  });
 }