feat(protocol): negotiate display and native input

tools/validate_gateway_envelopes.py

@@ -37,6 +37,13 @@ def classify_input(raw: bytes) -> str:
             return "invalid:field"
         active_mask = int.from_bytes(body[1:3], "big")
         return "valid" if active_mask or not any(body[3:]) else "invalid:field"
+    if kind == 6:
+        if len(body) != 8:
+            return "invalid:length"
+        x, y, width, height = (int.from_bytes(body[index:index + 2], "big") for index in range(0, 8, 2))
+        return "valid" if width and height and x < width and y < height else "invalid:field"
+    if kind == 7:
+        return "valid" if len(body) == 4 else "invalid:length"
     return "invalid:kind"