doc: clarify Worker execArgv vs Permission Model grants

doc/api/permissions.md

@@ -330,7 +330,13 @@ easy to configure permissions as needed when using `npx`.
 
 There are constraints you need to know before using this system:
 
-* The model does not inherit to a worker thread.
+* The model does not inherit to a worker thread. A default
+  `worker_threads.Worker` (no `execArgv` option) still receives the parent
+  process CLI flags, including `--permission` and `--allow-*` if those were
+  passed to the parent. Setting `execArgv` explicitly, including
+  `execArgv: []`, replaces the inherited flags. The worker then does not keep
+  the parent's Permission Model grants unless those flags are listed again in
+  `execArgv`. That difference is intended, not a bypass.
 * When using the Permission Model the following features will be restricted:
   * Native modules
   * Network

doc/api/worker_threads.md

@@ -1631,6 +1631,12 @@ changes:
     process (such as `--title`) are not supported. If set, this is provided
     as [`process.execArgv`][] inside the worker. By default, options are
     inherited from the parent thread.
+    Passing an explicit `execArgv` (including an empty array) replaces that
+    inheritance: the worker receives only the listed flags. Under the
+    [Permission Model](permissions.md#permission-model), that means an explicit
+    `execArgv` can drop the parent's `--permission` / `--allow-*` grants.
+    Omit `execArgv` to keep the parent's CLI flags. This is intended. See
+    [Permission Model limitations](permissions.md#limitations-and-known-issues).
   * `stdin` {boolean} If this is set to `true`, then `worker.stdin`
     provides a writable stream whose contents appear as `process.stdin`
     inside the Worker. By default, no data is provided.