Add ARIA labels and keyboard navigation to interactive components

Background Stoplight is a circuit breaker. A "light" wraps a block of code and, based on measured failures, trips from green (calls run normally) to red (calls are rejected or fall back), later probing recovery through yellow. Where that state lives is the data store. Stoplight…

Problem Admin::Actions::Stats passes metrics.consecutive_errors to LightView as failure_count, and _card.erb labels it Failures. This is not a total failure count. It is the current consecutive failure streak; for windowed/error-rate lights it also omits the errors, requests, and…

Stoplight has an internal "telemetry bus": typed event objects get emitted at key moments (a run finishing, a color change, a lock toggling), and any code that subscribed to that event type is called with it. Emitter#emit already no-ops cheaply when nobody's subscribed, so…

Problem An unlocked red card says “Will attempt recovery after cooling period.” Operators cannot tell whether that period expires in seconds or minutes, whether it has already elapsed, or whether the light is manually locked and therefore will never recover automatically.…