Suggest brand IDs after brand: and place unknown-brand errors on their line

- Completion for brand values in .archify (YAML) and Archify JSON sources,
  from the bundled brand-marks/catalog.json (107 marks); aliases and
  product names match, so "kafka" offers apache-kafka
- brand/unknown diagnostics carry their JSON pointer only at the start of
  the message; use it when subject.path is missing, so the error lands on
  the brand line instead of the top of the file
- Unit tests for catalog loading, value detection and pointer fallback;
  integration checks for completion and diagnostic placement

Closes #5

test/integration/suite.ts

@@ -131,6 +131,54 @@ export async function run(): Promise<void> {
     );
   });
 
+  await check('suggests brand IDs after brand: in .archify files', async () => {
+    const target = workspaceFile('brands.archify');
+    const text = [
+      'schema_version: 1',
+      'diagram_type: architecture',
+      'meta:',
+      '  title: Brands',
+      'components:',
+      '  - id: db',
+      '    type: database',
+      '    label: DB',
+      '    brand: ',
+      '  - id: bus',
+      '    type: messagebus',
+      '    label: Bus',
+      '    brand: kafka',
+      '',
+    ].join('\n');
+    await vscode.workspace.fs.writeFile(target, new TextEncoder().encode(text));
+    const doc = await vscode.workspace.openTextDocument(target);
+    const labels = async (line: number) => {
+      const list = await vscode.commands.executeCommand<vscode.CompletionList>(
+        'vscode.executeCompletionItemProvider',
+        doc.uri,
+        new vscode.Position(line, doc.lineAt(line).text.length),
+      );
+      return list.items.map((item) => (typeof item.label === 'string' ? item.label : item.label.label));
+    };
+    const empty = await labels(8);
+    assert.ok(empty.includes('postgresql') && empty.includes('redis'), 'brand IDs offered after "brand: "');
+    const kafka = await labels(12);
+    assert.ok(kafka.includes('apache-kafka'), 'the alias "kafka" finds apache-kafka');
+    assert.equal((await labels(7)).includes('postgresql'), false, 'nothing offered for other fields');
+  });
+
+  await check('an unknown brand is reported on its own line', async () => {
+    const target = workspaceFile('unknown-brand.archify');
+    const text = new TextDecoder().decode(await vscode.workspace.fs.readFile(workspaceFile('web-platform.archify')))
+      .replace(/^( {2}- id: [^\n]+\n)/m, '$1    brand: not-a-brand\n');
+    await vscode.workspace.fs.writeFile(target, new TextEncoder().encode(text));
+    const doc = await vscode.workspace.openTextDocument(target);
+    await vscode.window.showTextDocument(doc);
+    const diagnostic = await waitFor('brand/unknown diagnostic', () =>
+      vscode.languages.getDiagnostics(doc.uri).find((d) => d.source === 'archify' && d.code === 'brand/unknown'),
+    );
+    assert.match(doc.lineAt(diagnostic.range.start.line).text, /brand: not-a-brand/);
+  });
+
   await check('opens a live preview beside the source', async () => {
     await vscode.commands.executeCommand('archify.showPreviewToSide', workspaceFile('production-deployment.architecture.json'));
     const tabs = await waitFor('preview tab', () => {