test: deflake async-hooks statwatcher test

Wait for the initial missing-file poll before writing watched files.
Otherwise uv_fs_poll can observe the created file as its baseline and
never emit the expected change event.
Signed-off-by: Kamat, Trivikram <16024985+trivikr@users.noreply.github.com>
Assisted-by: openai:gpt-5.5
PR-URL: #63396
Refs: https://github.com/nodejs/reliability/blob/main/reports/2026-05-15.md#jstest-failure
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>

Author: trivikr

test/async-hooks/test-statwatcher.js

@@ -59,10 +59,32 @@ checkInvocations(statwatcher1, { init: 1 },
 'watcher1: when started to watch second file');
 checkWatcherStart('watcher2',statwatcher2);
 
-setTimeout(()=>fs.writeFileSync(file1,'foo++'),
-common.platformTimeout(100));
+letw2Initialized=false;
+letwriteFile2AfterW1=false;
+
+constonW2Initialized=(curr,prev)=>{
+if(curr.nlink!==0||prev.nlink!==0)
+return;
+
+w2.removeListener('change',onW2Initialized);
+w2Initialized=true;
+if(writeFile2AfterW1){
+setTimeout(()=>fs.writeFileSync(file2,'bar++'),
+common.platformTimeout(100));
+}
+};
+w2.on('change',onW2Initialized);
+
 w1.on('change',common.mustCallAtLeast((curr,prev)=>{
 console.log('w1 change to',curr,'from',prev);
+// Wait for the initial ENOENT poll before creating the file. Otherwise the
+// first stat can race with the write and use the created file as the baseline.
+if(curr.nlink===0&&prev.nlink===0){
+setTimeout(()=>fs.writeFileSync(file1,'foo++'),
+common.platformTimeout(100));
+return;
+}
+
 // Wait until we get the write above.
 if(prev.size!==0||curr.size!==5)
 return;
@@ -74,8 +96,11 @@ w1.on('change', common.mustCallAtLeast((curr, prev) => {
 checkInvocations(statwatcher2,{init: 1},
 'watcher2: when unwatched first file');
 
-setTimeout(()=>fs.writeFileSync(file2,'bar++'),
-common.platformTimeout(100));
+writeFile2AfterW1=true;
+if(w2Initialized){
+setTimeout(()=>fs.writeFileSync(file2,'bar++'),
+common.platformTimeout(100));
+}
 w2.on('change',common.mustCallAtLeast((curr,prev)=>{
 console.log('w2 change to',curr,'from',prev);
 // Wait until we get the write above.