docs: replace removed session.idle.backgroundTasks field with the current aborted field (#2232)

The `session.idle` reference tables listed a `backgroundTasks` field of type
`BackgroundTasks`. That field was removed from the payload and the docs were
never updated; the type name no longer exists in the schema either. The
payload's only member today is an optional `aborted` boolean, which was
undocumented.

Corrects the data-field row and the at-a-glance row in
docs/features/streaming-events.md, plus the two Node.js quick-reference
tables. Documentation only; no code, schema or generated file is affected.

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

Author: examon

docs/features/streaming-events.md

@@ -548,7 +548,7 @@ Ephemeral. The agent has finished all processing and is ready for the next messa
 
 | Data Field | Type | Required | Description |
 |------------|------|----------|-------------|
-| `backgroundTasks` | `BackgroundTasks` | | Background agents/shells still running when the agent became idle |
+| `aborted` | `boolean` | | True when the preceding turn was cancelled via abort signal |
 
 ### `session.error`
 
@@ -958,7 +958,7 @@ This table lists key `data` payload fields. Common envelope fields are documente
 | `tool.execution_partial_result` | ✅ | Tool | `toolCallId`, `partialOutput` |
 | `tool.execution_progress` | ✅ | Tool | `toolCallId`, `progressMessage` |
 | `tool.execution_complete` | | Tool | `toolCallId`, `success`, `result?`, `error?` |
-| `session.idle` | ✅ | Session | `backgroundTasks?` |
+| `session.idle` | ✅ | Session | `aborted?` |
 | `session.error` | | Session | `errorType`, `message`, `statusCode?` |
 | `session.compaction_start` | | Session | *(empty)* |
 | `session.compaction_complete` | | Session | `success`, `preCompactionTokens?`, `summaryContent?` |

nodejs/docs/agent-author.md

@@ -270,7 +270,7 @@ const unsub = session.on("tool.execution_complete", (event) => {
 | `tool.execution_start`    | `toolCallId`, `toolName`, `arguments`                  |
 | `tool.execution_complete` | `toolCallId`, `success`, `result`, `error`             |
 | `user.message`            | `content`, `attachments`, `source`                     |
-| `session.idle`            | `backgroundTasks`                                      |
+| `session.idle`            | `aborted`                                              |
 | `session.error`           | `errorType`, `message`, `stack`                        |
 | `permission.requested`    | `requestId`, `permissionRequest.kind`                  |
 | `session.shutdown`        | `shutdownType`, `totalPremiumRequests`                 |

nodejs/docs/examples.md

@@ -419,7 +419,7 @@ session.on("assistant.message", (event) => {
 | `tool.execution_start`      | A tool is about to run                           | `toolCallId`, `toolName`, `arguments`                  |
 | `tool.execution_complete`   | A tool finished running                          | `toolCallId`, `success`, `result`, `error`             |
 | `user.message`              | User sent a message                              | `content`, `attachments`, `source`                     |
-| `session.idle`              | Session finished processing a turn               | `backgroundTasks`                                      |
+| `session.idle`              | Session finished processing a turn               | `aborted`                                              |
 | `session.error`             | An error occurred                                | `errorType`, `message`, `stack`                        |
 | `permission.requested`      | Agent needs permission (shell, file write, etc.) | `requestId`, `permissionRequest.kind`                  |
 | `session.shutdown`          | Session is ending                                | `shutdownType`, `totalPremiumRequests`, `codeChanges`  |