Why: spans now follow the OTel GenAI convention (Agent-Native#32); the
product needs the settings surface for the exporter, a meaningful
service.name, and per-profile agent names.
Evidence: go test -count=1 ./... green; TestTelemetryFlagsDefaults
(otlpEndpoint registered default empty = no export, serviceName
default agent-system-backend); nested pins carry the convention work.
Impact: nothing is exported unless telemetry.otlpEndpoint (or the env
var) is set; agent spans are named by profile id.
Refs: Agent-Native#32, Agent-Squad#36, N3 plan WP4