test: apply a delay to watch-mode-kill-signal tests

The test is still flaking on macOS. This might be caused by fs
event coalescing. Apply a delay to reduce the chance of it.
Also, add a bit more logs to show more information.

PR-URL: #60610
Refs: https://github.com/nodejs/reliability/blob/main/reports/2025-11-07.md
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>

Author: joyeecheung

test/fixtures/kill-signal-for-watch.js

@@ -7,4 +7,7 @@ process.on('SIGINT', () => {
   process.exit();
 });
 process.send(`script ready ${process.pid}`);
-setTimeout(() => {}, 100_000);
+const timeout = 100_000;
+setTimeout(() => {
+  process._rawDebug(`[CHILD] Timeout ${timeout} fired`);
+}, timeout);

test/parallel/test-watch-mode-kill-signal-default.mjs

@@ -51,7 +51,12 @@ child.on('message', (msg) => {
     const match = msg.match(/script ready (\d+)/);
     if (match) {
       firstGrandchildPid = match[1];  // This is the first grandchild
-      writeFileSync(indexPath, indexContents);
+      const writeDelay = 1000;  // Delay to reduce the chance of fs events coalescing
+      console.log(`[PARENT] writing to restart ${firstGrandchildPid} after ${writeDelay}ms`);
+      setTimeout(() => {
+        console.log(`[PARENT] writing to ${indexPath} to restart ${firstGrandchildPid}`);
+        writeFileSync(indexPath, indexContents);
+      }, writeDelay);
     }
   }
 });

test/parallel/test-watch-mode-kill-signal-override.mjs

@@ -52,7 +52,12 @@ child.on('message', (msg) => {
     const match = msg.match(/script ready (\d+)/);
     if (match) {
       firstGrandchildPid = match[1];  // This is the first grandchild
-      writeFileSync(indexPath, indexContents);
+      const writeDelay = 1000;  // Delay to reduce the chance of fs events coalescing
+      console.log(`[PARENT] writing to restart ${firstGrandchildPid} after ${writeDelay}ms`);
+      setTimeout(() => {
+        console.log(`[PARENT] writing to ${indexPath} to restart ${firstGrandchildPid}`);
+        writeFileSync(indexPath, indexContents);
+      }, writeDelay);
     }
   }
 });