TUI Experiments

Temporary, opt-in UI experiments belong in the experiments registry in src/component/dialog-experiments.tsx, with behavior gated by the matching config.experimental key.
The Experiments framework is permanent infrastructure. Keep the registry, dialog, settings persistence, toggle handling, and UI entry point even when there are no active experiments.
Graduating an experiment means removing only its registry entry and feature-specific gate, making that feature's behavior unconditional. Abandoning an experiment means removing its entry, gate, and experimental behavior.
Do not remove or simplify away the reusable Experiments infrastructure because the registry is empty. An empty registry is intentional and ready for future experiments, not dead code.