Remove the legacy EventKind/Event envelope mapping and let agent event emission build pkg/events.Event values directly.
Keep HookMeta as the shared hook metadata shape and preserve legacy observe string aliases by mapping them to runtime event kinds.
Validation: GOCACHE=/tmp/picoclaw-go-cache go test ./pkg/agent; make lint
Introduce pkg/events with filtered channels, subscription policies, backpressure, and stats. Wire AgentLoop to dual-publish legacy agent events into runtime events while preserving old event APIs.
Validation: go test ./pkg/events/... ./pkg/agent; go test -race ./pkg/events/...; make lint