watch: track worker thread entry files in --watch mode

Currently, --watch mode only tracks dependencies from the main module graph
(require/import). Worker thread entry points created via new Worker() are not
included, so changes to worker files do not trigger restarts.

This change hooks into Worker initialization and registers the worker entry
file with the watch mode, ensuring restarts when worker files change.

Fixes: #62275

Author: SudhansuBandha

lib/internal/watch_mode/files_watcher.js

@@ -179,6 +179,9 @@ class FilesWatcher extends EventEmitter {
         if (ArrayIsArray(message['watch:import'])) {
           ArrayPrototypeForEach(message['watch:import'], (file) => this.filterFile(fileURLToPath(file), key));
         }
+        if (ArrayIsArray(message['watch:worker'])) {
+           ArrayPrototypeForEach(message['watch:worker'], (file) => this.filterFile(file, key));
+        }
       } catch {
         // Failed watching file. ignore
       }

lib/internal/worker.js

@@ -195,6 +195,17 @@ class HeapProfileHandle {
   }
 }
 
+/**
+ * Tell the watch mode that a worker file was instantiated.
+ * @param {string} filename Absolute path of the worker file
+ * @returns {void}
+ */
+function reportWorkerToWatchMode(filename) {
+  if (process.env.WATCH_REPORT_DEPENDENCIES && process.send) {
+    process.send({ 'watch:worker': [filename] });
+  }
+}
+
 class Worker extends EventEmitter {
   constructor(filename, options = kEmptyObject) {
     throwIfBuildingSnapshot('Creating workers');
@@ -275,6 +286,11 @@ class Worker extends EventEmitter {
       name = StringPrototypeTrim(options.name);
     }
 
+    // Report to watch mode if this is a regular file (not eval, internal, or data URL)
+    if (!isInternal && doEval === false) {
+      reportWorkerToWatchMode(filename);
+    }
+
     debug('instantiating Worker.', `url: ${url}`, `doEval: ${doEval}`);
     // Set up the C++ handle for the worker, as well as some internal wiring.
     this[kHandle] = new WorkerImpl(url,