chore(RECIPE-0004): complete iteration 1 — fix TypeScript Timer type errors

- Fixed NodeJS.Timer → NodeJS.Timeout in scheduler.ts line 13
- Fixed NodeJS.Timer[] → NodeJS.Timeout[] in fixtures.ts line 151
- Resolves TypeScript compile errors from iteration 0 review
- All 260 tests passing, build succeeds with no errors

src/tests/fixtures.ts

@@ -148,7 +148,7 @@ export const testFixtures = {
  * Helper to create a spy for interval/timeout functions
  */
 export const createTimerSpy = () => {
-	let timers: NodeJS.Timer[] = [];
+	let timers: NodeJS.Timeout[] = [];
 
 	return {
 		setInterval: (callback: () => void, ms: number) => {