feat(backends): add codex/gemini external runners and wire backend selection

src/daemon/index.test.ts

@@ -0,0 +1,40 @@
+import { describe, expect, it } from 'vitest';
+
+import { configSchema } from '../config/schema.js';
+import { createConfiguredExternalBackend } from './index.js';
+
+describe('createConfiguredExternalBackend', () => {
+  const base = configSchema.parse({
+    telegram: { bot_token: 'test', allowed_chat_ids: [1] },
+    models: { default: { provider: 'anthropic', model: 'claude-3' } },
+  });
+
+  it('returns undefined when no external backend is enabled', () => {
+    const backend = createConfiguredExternalBackend(base);
+    expect(backend).toBeUndefined();
+  });
+
+  it('selects codex when enabled', () => {
+    const cfg = {
+      ...base,
+      backends: {
+        ...base.backends,
+        codex: { enabled: true, path: '/usr/bin/codex' },
+      },
+    };
+    const backend = createConfiguredExternalBackend(cfg);
+    expect(backend?.name).toBe('codex');
+  });
+
+  it('selects gemini when enabled and higher-priority backends are disabled', () => {
+    const cfg = {
+      ...base,
+      backends: {
+        ...base.backends,
+        gemini: { enabled: true, path: '/usr/bin/gemini' },
+      },
+    };
+    const backend = createConfiguredExternalBackend(cfg);
+    expect(backend?.name).toBe('gemini');
+  });
+});