feat(server): expose progress_callback on ServerSession request methods

Add progress_callback parameter to create_message(), elicit_form(),
elicit_url(), and the deprecated elicit() wrapper so that server code
can receive bidirectional progress notifications from the client during
sampling and elicitation requests.

BaseSession.send_request() already supports progress_callback, but none
of the ServerSession convenience methods forwarded it — callers had no
way to pass the parameter without dropping down to send_request().

Closes #1650

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: g97iulio1609

src/mcp/server/session.py

@@ -46,6 +46,7 @@ async def handle_list_prompts(ctx: RequestContext, params) -> ListPromptsResult:
 from mcp.shared.message import ServerMessageMetadata, SessionMessage
 from mcp.shared.session import (
     BaseSession,
+    ProgressFnT,
     RequestResponder,
 )
 from mcp.shared.version import SUPPORTED_PROTOCOL_VERSIONS
@@ -245,6 +246,7 @@ async def create_message(
         tools: None = None,
         tool_choice: types.ToolChoice | None = None,
         related_request_id: types.RequestId | None = None,
+        progress_callback: ProgressFnT | None = None,
     ) -> types.CreateMessageResult:
         """Overload: Without tools, returns single content."""
         ...
@@ -264,6 +266,7 @@ async def create_message(
         tools: list[types.Tool],
         tool_choice: types.ToolChoice | None = None,
         related_request_id: types.RequestId | None = None,
+        progress_callback: ProgressFnT | None = None,
     ) -> types.CreateMessageResultWithTools:
         """Overload: With tools, returns array-capable content."""
         ...
@@ -282,6 +285,7 @@ async def create_message(
         tools: list[types.Tool] | None = None,
         tool_choice: types.ToolChoice | None = None,
         related_request_id: types.RequestId | None = None,
+        progress_callback: ProgressFnT | None = None,
     ) -> types.CreateMessageResult | types.CreateMessageResultWithTools:
         """Send a sampling/create_message request.
 
@@ -338,11 +342,13 @@ async def create_message(
                 request=request,
                 result_type=types.CreateMessageResultWithTools,
                 metadata=metadata_obj,
+                progress_callback=progress_callback,
             )
         return await self.send_request(
             request=request,
             result_type=types.CreateMessageResult,
             metadata=metadata_obj,
+            progress_callback=progress_callback,
         )
 
     async def list_roots(self) -> types.ListRootsResult:
@@ -359,6 +365,7 @@ async def elicit(
         message: str,
         requested_schema: types.ElicitRequestedSchema,
         related_request_id: types.RequestId | None = None,
+        progress_callback: ProgressFnT | None = None,
     ) -> types.ElicitResult:
         """Send a form mode elicitation/create request.
 
@@ -374,13 +381,14 @@ async def elicit(
             This method is deprecated in favor of elicit_form(). It remains for
             backward compatibility but new code should use elicit_form().
         """
-        return await self.elicit_form(message, requested_schema, related_request_id)
+        return await self.elicit_form(message, requested_schema, related_request_id, progress_callback=progress_callback)
 
     async def elicit_form(
         self,
         message: str,
         requested_schema: types.ElicitRequestedSchema,
         related_request_id: types.RequestId | None = None,
+        progress_callback: ProgressFnT | None = None,
     ) -> types.ElicitResult:
         """Send a form mode elicitation/create request.
 
@@ -406,6 +414,7 @@ async def elicit_form(
             ),
             types.ElicitResult,
             metadata=ServerMessageMetadata(related_request_id=related_request_id),
+            progress_callback=progress_callback,
         )
 
     async def elicit_url(
@@ -414,6 +423,7 @@ async def elicit_url(
         url: str,
         elicitation_id: str,
         related_request_id: types.RequestId | None = None,
+        progress_callback: ProgressFnT | None = None,
     ) -> types.ElicitResult:
         """Send a URL mode elicitation/create request.
 
@@ -444,6 +454,7 @@ async def elicit_url(
             ),
             types.ElicitResult,
             metadata=ServerMessageMetadata(related_request_id=related_request_id),
+            progress_callback=progress_callback,
         )
 
     async def send_ping(self) -> types.EmptyResult:  # pragma: no cover