fix(runners): run after_run_callback when an aborted run is cancelled

[abhayjoshi201]

Link to Issue or Description of Change

1. Link to an existing issue (if applicable):

• Closes: after_run_callback is not called when the task driving Runner.run_async is cancelled (regression in 2.11.0) #7394

Problem:
When an invocation is aborted via abort_signal and the task driving Runner.run_async is cancelled (such as on POST /run_sse client disconnect, where abort_signal.set() and producer_task.cancel() are called in the same turn), Runner._exec_with_plugin and run_node_async treated asyncio.CancelledError as an unhandled run_error unless _CALLER_CLOSED_EARLY_MSG was passed. As a result, after_run_callback was skipped in the finally block even though invocation_context.is_aborted was True and dangling function calls were sealed.

Additionally, POST /run in src/google/adk/cli/api_server.py did not pass or trip abort_signal in its http.disconnect monitor before calling worker_task.cancel(), so client disconnects on /run neither sealed dangling function calls (INVOCATION_ABORTED) nor executed after_run_callback.

Solution:

1. In Runner._exec_with_plugin (src/google/adk/runners.py) and run_node_async (src/google/adk/workflow/_node_runner_utils.py), treat asyncio.CancelledError when invocation_context.is_aborted (ic.is_aborted) is True as an early close (closing_early = True, leaving run_error = None) so after_run_callback executes after sealing any dangling function calls.
2. In POST /run (src/google/adk/cli/api_server.py), pass abort_signal to runner.run_async(...) and call abort_signal.set() before worker_task.cancel() on http.disconnect, matching POST /run_sse.

Testing Plan

Unit Tests:

• I have added or updated unit tests for my change.
• All unit tests pass locally.

pytest tests/unittests/test_runners.py tests/unittests/cli/test_fast_api.py tests/unittests/workflow/test_workflow.py tests/unittests/plugins/test_notification_error_callbacks.py
460 passed, 5 skipped, 1 xfailed in 36.77s

Manual End-to-End (E2E) Tests:

Verified with SlowToolAgent and _AfterRunPlugin across Runner.run_async, POST /run, and POST /run_sse that disconnecting a client or cancelling an aborted invocation task seals dangling FunctionCalls with INVOCATION_ABORTED and executes after_run_callback.

Checklist

• I have read the CONTRIBUTING.md document.
• I have performed a self-review of my own code.
• I have commented my code, particularly in hard-to-understand areas.
• I have added tests that prove my fix is effective or that my feature works.
• New and existing unit tests pass locally with my changes.
• I have manually tested my changes end-to-end.
• Any dependent changes have been merged and published in downstream modules.