refactor(server)!: remove Starlette and FastAPI utilities and rely only on routes

src/a2a/compat/v0_3/jsonrpc_adapter.py

@@ -10,8 +10,8 @@
 if TYPE_CHECKING:
     from starlette.requests import Request
 
-    from a2a.server.apps.jsonrpc.jsonrpc_app import CallContextBuilder
     from a2a.server.request_handlers.request_handler import RequestHandler
+    from a2a.server.routes.jsonrpc_dispatcher import CallContextBuilder
     from a2a.types.a2a_pb2 import AgentCard
 
     _package_starlette_installed = True

src/a2a/compat/v0_3/rest_adapter.py

@@ -33,12 +33,11 @@
 
 from a2a.compat.v0_3 import conversions
 from a2a.compat.v0_3.rest_handler import REST03Handler
-from a2a.server.apps.jsonrpc.jsonrpc_app import (
+from a2a.server.context import ServerCallContext
+from a2a.server.routes.jsonrpc_dispatcher import (
     CallContextBuilder,
     DefaultCallContextBuilder,
 )
-from a2a.server.apps.rest.rest_adapter import RESTAdapterInterface
-from a2a.server.context import ServerCallContext
 from a2a.utils.error_handlers import (
     rest_error_handler,
     rest_stream_error_handler,
@@ -53,7 +52,7 @@
 logger = logging.getLogger(__name__)
 
 
-class REST03Adapter(RESTAdapterInterface):
+class REST03Adapter:
     """Adapter to make RequestHandler work with v0.3 RESTful API.
 
     Defines v0.3 REST request processors and their routes, as well as managing response generation including Server-Sent Events (SSE).