feat: TypeScript installation wizard with @clack/prompts TUI (#1)

Co-authored-by: Jason Woltje <jason@diversecanvas.com>
Co-committed-by: Jason Woltje <jason@diversecanvas.com>

tests/template/engine.test.ts

@@ -0,0 +1,52 @@
+import { describe, it, expect } from 'vitest';
+import { renderTemplate } from '../../src/template/engine.js';
+
+describe('renderTemplate', () => {
+  it('replaces all placeholders', () => {
+    const template = 'You are **{{AGENT_NAME}}**, role: {{ROLE_DESCRIPTION}}';
+    const result = renderTemplate(template, {
+      AGENT_NAME: 'Jarvis',
+      ROLE_DESCRIPTION: 'steward',
+    });
+    expect(result).toBe('You are **Jarvis**, role: steward');
+  });
+
+  it('preserves ${ENV_VAR} references', () => {
+    const template = 'Path: ${HOME}/.config, Agent: {{AGENT_NAME}}';
+    const result = renderTemplate(template, { AGENT_NAME: 'Test' });
+    expect(result).toBe('Path: ${HOME}/.config, Agent: Test');
+  });
+
+  it('handles multi-line values', () => {
+    const template = '{{PRINCIPLES}}';
+    const result = renderTemplate(template, {
+      PRINCIPLES: '1. First\n2. Second\n3. Third',
+    });
+    expect(result).toBe('1. First\n2. Second\n3. Third');
+  });
+
+  it('replaces unset vars with empty string by default', () => {
+    const template = 'Before {{MISSING}} After';
+    const result = renderTemplate(template, {});
+    expect(result).toBe('Before  After');
+  });
+
+  it('throws in strict mode for missing vars', () => {
+    const template = '{{MISSING}}';
+    expect(() => renderTemplate(template, {}, { strict: true })).toThrow(
+      'Template variable not provided: {{MISSING}}',
+    );
+  });
+
+  it('handles multiple occurrences of same placeholder', () => {
+    const template = '{{NAME}} says hello, {{NAME}}!';
+    const result = renderTemplate(template, { NAME: 'Jarvis' });
+    expect(result).toBe('Jarvis says hello, Jarvis!');
+  });
+
+  it('preserves non-placeholder curly braces', () => {
+    const template = 'const x = { foo: {{VALUE}} }';
+    const result = renderTemplate(template, { VALUE: '"bar"' });
+    expect(result).toBe('const x = { foo: "bar" }');
+  });
+});