feat(api): support asImage=true on screen and zoom

docs/API.md

@@ -22,8 +22,9 @@ Query params:
 - `include_labels` (bool, default `true`)
 - `image_format` (`png`|`jpeg`, default `png`)
 - `jpeg_quality` (1-100, default `85`)
+- `asImage` (bool, default `false`) — if `true`, return raw image bytes only (`image/png` or `image/jpeg`)
 
-Response includes base64 image and metadata (`meta.region`, optional `meta.grid`).
+Default response includes base64 image and metadata (`meta.region`, optional `meta.grid`).
 
 ## `POST /zoom`
 
@@ -44,7 +45,11 @@ Body:
 }
 ```
 
-Returns cropped image + region metadata in global pixel coordinates.
+Query params:
+
+- `asImage` (bool, default `false`) — if `true`, return raw image bytes only (`image/png` or `image/jpeg`)
+
+Default response returns cropped image + region metadata in global pixel coordinates.
 
 ## `POST /action`