Implements graceful suppression of transient `task.json` ENOENT errors in the executor, logging a suppression signal and surfacing a banner in the UI, with test coverage for both the executor behavior and notification service. Documentation in `docs/architecture.md` and a changeset for `@runfusion/f Fusion-Task-Id: FN-5624 Co-authored-by: Fusion (runfusion.ai) <noreply@runfusion.ai> Fusion-Task-Id: FN-5624