Fix SessionHttpContext to delegate attributes via __getattr__

The previous implementation eagerly copied ASGI-specific attributes
(pathsend, receive, send) from the wrapped context, which crashed under
RSGI because RsgiContext does not have those attributes. Now
SessionHttpContext delegates all non-overridden attributes to the wrapped
context via __getattr__, making it protocol-agnostic.

packages/kaya-session/src/kaya/session/_mixin.py

@@ -15,6 +15,10 @@ class SessionHttpContext(HttpContext):
 
     Works with any concrete ``HttpContext`` (ASGI or RSGI) because it only
     relies on the abstract send methods, which all implementations share.
+    Attributes not explicitly overridden are delegated to the wrapped context
+    via ``__getattr__``, so protocol-specific fields (``pathsend``,
+    ``receive``/``send`` for ASGI, ``protocol`` for RSGI, etc.) are passed
+    through transparently.
     """
 
     def __init__(
@@ -23,20 +27,14 @@ class SessionHttpContext(HttpContext):
         session: Session,
         cookie_injector: Callable[[], Optional[str]],
     ) -> None:
-        self._ctx = ctx
-        self.session = session
-        self._cookie_injector = cookie_injector
-        self.pathsend = ctx.pathsend
-        self.receive = ctx.receive
-        self.send = ctx.send
-        self.scheme = ctx.scheme
-        self.method = ctx.method
-        self.path = ctx.path
-        self.query_string = ctx.query_string
-        self.headers = ctx.headers
-        self.client = ctx.client
-        self.server = ctx.server
-        self.request_body = ctx.request_body
+        object.__setattr__(self, '_ctx', ctx)
+        object.__setattr__(self, 'session', session)
+        object.__setattr__(self, '_cookie_injector', cookie_injector)
+
+    def __getattr__(self, name: str) -> Any:
+        if name == '_ctx':
+            raise AttributeError(name)
+        return getattr(self._ctx, name)
 
     def _inject_cookie(self, headers: Optional[Mapping[str, StrOrStrings]]) -> Optional[Mapping[str, StrOrStrings]]:
         cookie_value = self._cookie_injector()