fix(cutover): track direct detached listener pid

apps/api/src/production-gateway.test.ts

@@ -45,9 +45,9 @@ async function fixture(name = 'cutover'): Promise<CutoverPlan> {
     drillEvidence: drill,
     drillEvidenceSha256: createHash('sha256').update(drillContent).digest('hex'),
     legacyPid: 41,
-    legacyCommand: '/usr/bin/true legacy',
+    legacyCommand: '/usr/local/bin/node /absolute/legacy/server.js',
     legacyIdentity: 'legacy-start-1',
-    legacyStart: ['/usr/bin/true', 'legacy'],
+    legacyStart: ['/usr/local/bin/node', '/absolute/legacy/server.js'],
     stateDir: join(root, 'state'),
   };
 }
@@ -134,7 +134,7 @@ describe('cutover validation and reversible orchestration', () => {
     expect(await readFile(statePath, 'utf8')).not.toContain(token);
     expect(await rollback(plan, system)).toBe(43);
     expect(signals).toEqual([41, 42]);
-    expect(starts[1]?.argv).toEqual(['/usr/bin/true', 'legacy']);
+    expect(starts[1]?.argv).toEqual(['/usr/local/bin/node', '/absolute/legacy/server.js']);
   });
 
   it('automatically restarts legacy if the gateway fails to own authenticated 8788', async () => {
@@ -149,7 +149,7 @@ describe('cutover validation and reversible orchestration', () => {
         resolve(process.cwd(), 'node_modules/.pnpm/tsx@4.22.4/node_modules/tsx/dist/loader.mjs'),
         resolve(process.cwd(), 'apps/api/src/production-gateway-cli.ts'),
       ],
-      ['/usr/bin/true', 'legacy'],
+      ['/usr/local/bin/node', '/absolute/legacy/server.js'],
     ]);
     const state = JSON.parse(await readFile(join(plan.stateDir, 'cutover-state.json'), 'utf8')) as {
       phase: string;