Fix agent-run tasks incorrectly prompting user with "press any key" input request (#301536)

* Initial plan

* Fix agent-run tasks incorrectly prompting "press any key" input request

Remove the `isTaskInactive` check in `OutputMonitor._handleIdleState()`.
When the execution is a task and the output contains a VS Code task finish
message, always treat it as a stop signal regardless of the task's active
state (which can be stale from `getBusyTasks()`). The generic "press any
key" prompt is now only shown for non-task executions.

Co-authored-by: meganrogge <[email protected]>

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Co-authored-by: copilot-swe-agent[bot] <[email protected]>
Co-authored-by: meganrogge <[email protected]>