Reject invalid TaskInstance state update payloads

[henry3260]

Why

I found The Execution API /execution/task-instances/{task_instance_id}/state endpoint previously exposed a catch-all TaskInstance state payload schema that allowed scheduler/executor- owned states such as scheduled, queued, and restarting.

Those states are not valid worker-reported execution outcomes for this endpoint. Since the route implementation does not handle them, sending one could fall through to an error path and potentially mark a running task as failed instead of rejecting the invalid payload.

we should block them in schema stage and return 422, we may not want them to change to FAIL

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