The execute prompt told the handler to wait with timeoutSeconds up to 170 -- a
leftover from the retired MCP_TOOL_TIMEOUT=200000ms era. The real server-side
clamp is TaskWaitMcpTools.MaxTimeoutSeconds = 900 and every launcher sets
930000ms, so the handler was making ~5x the wait_for_task_change calls it needed
and burning turns on re-waiting.
It also never passed treatWaitingForChildrenAsBusy, and only waited on ids that
were Queued or Running. A task with children reports "changed" the moment it
reaches WaitingForChildren, so such a task both dropped out of the wait set and
signalled completion early -- the handler could reach review/merge while
children were still running.