feat(cli): add VS Code extension wrapping glint lsp

editors/vscode/ is a TypeScript VS Code extension that starts glint lsp
as a child process and connects to it via vscode-languageclient. The
documentSelector restricts LSP processing to **/.gitlab-ci.yml so other
YAML files are unaffected. The glint.executablePath setting controls the
binary location (default: glint on PATH). Build with task ext-compile;
package as .vsix with task ext-package. Taskfile tasks added:
ext-install, ext-compile, ext-package. Root .gitignore updated to
exclude node_modules/, out/, and *.vsix from the extension directory.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

editors/vscode/src/extension.ts

@@ -0,0 +1,41 @@
+import * as vscode from 'vscode';
+import {
+  LanguageClient,
+  LanguageClientOptions,
+  ServerOptions,
+  TransportKind,
+} from 'vscode-languageclient/node';
+
+let client: LanguageClient | undefined;
+
+export function activate(context: vscode.ExtensionContext): void {
+  const cfg = vscode.workspace.getConfiguration('glint');
+  const glintPath = cfg.get<string>('executablePath') || 'glint';
+
+  const serverOptions: ServerOptions = {
+    command: glintPath,
+    args: ['lsp'],
+    transport: TransportKind.stdio,
+  };
+
+  const clientOptions: LanguageClientOptions = {
+    // Only process .gitlab-ci.yml files, not all YAML.
+    documentSelector: [
+      { scheme: 'file', language: 'yaml', pattern: '**/.gitlab-ci.yml' },
+    ],
+  };
+
+  client = new LanguageClient(
+    'glint',
+    'glint — GitLab CI Linter',
+    serverOptions,
+    clientOptions,
+  );
+
+  client.start();
+  context.subscriptions.push(client);
+}
+
+export async function deactivate(): Promise<void> {
+  await client?.stop();
+}