Orphaned background tasks are deduplicated before you are told about them

After a cloud worker restart, the lists of running tasks and tasks awaiting notification are merged through one shared deduplication helper instead of hand-written map merging, and if a task was still running an extra wait happens before the orphaned-task notice is shown. The component that restores MCP tasks is now also given the app-state setter, so restored tasks can write back into app state.