better comments

protobuf/video/sfu/models/models.proto

@@ -142,6 +142,20 @@ message PublishOption {
   // - Half resolution (2 layers) = 640x360
   // - Quarter resolution (3 layers) = 320x180
   VideoDimension video_dimension = 7;
+
+  // The unique identifier for the publish request.
+  // - This `id` is assigned exclusively by the SFU. Any `id` set by the client
+  //   in the `PublishOption` will be ignored and overwritten by the SFU.
+  // - The primary purpose of this `id` is to uniquely identify each publish
+  //   request, even in scenarios where multiple publish requests for the same
+  //   `track_type` and `codec` are active simultaneously.
+  //   For example:
+  //     - A user may publish two tracks of the same type (e.g., video) and codec
+  //       (e.g., VP9) concurrently.
+  // - This uniqueness ensures that individual requests can be managed
+  //   independently. For instance, an `id` is critical when stopping a specific
+  //   publish request without affecting others.
+  int32 id = 8;
 }
 
 message Codec {