feat: export A2UI types from public API (#125)

Export A2UiComponent and A2UiSurface from adcp.types module.
These types were added in beta2 schema sync but missing from exports.

Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

Author: bokelley

src/adcp/types/__init__.py

@@ -40,6 +40,8 @@
 # V3 Sponsored Intelligence types
 # V3 Governance (Property Lists) types
 from adcp.types._generated import (
+    A2UiComponent,
+    A2UiSurface,
     Account,
     ActivateSignalRequest,
     ActivateSignalResponse,
@@ -400,6 +402,8 @@
     "ValidateContentDeliveryRequest",
     "ValidateContentDeliveryResponse",
     # V3 Sponsored Intelligence
+    "A2UiComponent",
+    "A2UiSurface",
     "SiCapabilities",
     "SiGetOfferingRequest",
     "SiGetOfferingResponse",