Handle task completion notifications to skip polling delay

[Christian-Sidak]

Summary

Fixes #1037

When a server sends a notifications/tasks/status notification with a terminal status (completed, failed, or cancelled) for the task currently being polled, the inspector now immediately proceeds to fetch the result via tasks/get instead of waiting for the full poll interval to elapse.

Problem

The task polling loop in callTool used a fixed setTimeout with the server's pollInterval before each tasks/get call. Even when the server sent a notifications/tasks/status notification indicating the task was done, the inspector ignored it and kept sleeping until the timer expired. With long poll intervals, this caused a noticeable delay before the result appeared.

Approach

• Added a taskNotificationResolverRef that holds a { taskId, resolve } pair while the polling loop is active
• Modified the notifications/tasks/status handler to call resolve() when a terminal status arrives for the task being polled
• Replaced the polling loop's await new Promise(resolve => setTimeout(resolve, pollInterval)) with a Promise.race between the poll interval timer and the notification signal

This way, whichever comes first -- the poll interval elapsing or the notification arriving -- the loop proceeds to call tasks/get immediately.

Test plan

• All 515 existing tests pass
• Client builds successfully
• Manual: call a tool as a task against a server that sends notifications/tasks/status on completion; the result should appear immediately instead of waiting for the next poll cycle