test: fix coverage — remove unused handle_list_tools, mark else-branch

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: rudi193-cmd

tests/issues/test_1401_client_session_error_handling.py

@@ -55,21 +55,13 @@ async def test_transport_exception_unblocks_pending_request():
     """
     slow_tool_started = anyio.Event()
 
-    async def handle_list_tools(
-        ctx: ServerRequestContext, params: types.PaginatedRequestParams | None
-    ) -> types.ListToolsResult:
-        return types.ListToolsResult(
-            tools=[types.Tool(name="slow", description="hangs", input_schema={"type": "object"})]
-        )
-
     async def handle_call_tool(ctx: ServerRequestContext, params: CallToolRequestParams) -> CallToolResult:
         slow_tool_started.set()
         await anyio.sleep(60)  # hangs until cancelled
         return CallToolResult(content=[TextContent(type="text", text="never")])  # pragma: no cover
 
     server = Server(
         name="test",
-        on_list_tools=handle_list_tools,
         on_call_tool=handle_call_tool,
     )
 
@@ -118,7 +110,7 @@ async def test_custom_message_handler_receives_exception():
     received: list[Exception] = []
 
     async def capturing_handler(message: object) -> None:
-        if isinstance(message, Exception):
+        if isinstance(message, Exception):  # pragma: lax no cover
             received.append(message)  # capture — do not re-raise
 
     server_writer, server_reader = anyio.create_memory_object_stream[SessionMessage](4)