Update tasks/result to block until completion

Author: LucaButBoring

docs/specification/draft/basic/utilities/tasks.mdx

@@ -414,9 +414,9 @@ stateDiagram-v2
 ### Result Retrieval
 
 1. Receivers that accept a task-augmented request **MUST** return a `CreateTaskResult` as the response. This result **SHOULD** be returned as soon as possible after accepting the task.
-1. Receivers **MUST** only return the actual operation results via `tasks/result` when the task status is `completed`.
-1. Receivers **MUST** return an error if `tasks/result` is called for a task in any other status.
-1. Requestors **MAY** call `tasks/result` multiple times for the same task while it remains available.
+1. When a receiver receives a `tasks/result` request, it **MUST** block the response until the task reaches a terminal status (`completed`, `failed`, `cancelled`, or `unknown`).
+1. For tasks in `completed` status, receivers **MUST** return the actual operation results as specified by the original request type.
+1. For tasks in `failed`, `cancelled`, or `unknown` status, receivers **MUST** return a successful JSON-RPC response containing error or status details in the result structure.
 
 ### Associating Task-Related Messages
 
@@ -710,7 +710,6 @@ Receivers **MUST** return standard JSON-RPC errors for the following protocol er
 
 - Invalid or nonexistent `taskId` in `tasks/get`, `tasks/list`, `tasks/result`, or `tasks/delete`: `-32602` (Invalid params)
 - Invalid or nonexistent cursor in `tasks/list`: `-32602` (Invalid params)
-- Attempting to retrieve result when task is not in `completed` status: `-32602` (Invalid params)
 - Receiver rejects a `tasks/delete` request: `-32600` (Invalid request)
 - Internal errors: `-32603` (Internal error)
 
@@ -765,19 +764,6 @@ Receivers are not obligated to retain task metadata indefinitely. It is complian
 
 </Note>
 
-**Example: Result requested for incomplete task**
-
-```json
-{
-  "jsonrpc": "2.0",
-  "id": 72,
-  "error": {
-    "code": -32602,
-    "message": "Cannot retrieve result: Task status is 'working', not 'completed'"
-  }
-}
-```
-
 **Example: Task deletion rejected by receiver**
 
 ```json
@@ -810,7 +796,7 @@ When the underlying request does not complete successfully, the task moves to th
 }
 ```
 
-For tasks that wrap tool call requests, when the tool result has `isError` set to true, the task should reach `failed` status. The error information is conveyed both through the task's `failed` status and through the result structure when retrieved via `tasks/result`.
+For tasks that wrap tool call requests, when the tool result has `isError` set to true, the task should reach `failed` status.
 
 ## Security Considerations