The four telemetry gaps (rows on commits, chord.host, microsecond times, a read-only store) and: pages record and
send span batches over their link to the server's ingest object (checked, capped, rate-limited, stamped browser and
with the link's principal); workers send theirs too, so the server is the store's only writer; principalAttributes
lets an app choose what a span records about its principal. The tutorial shows a real page's click traced to the
worker, with the trace viewer.
defineMessages with typed t, t.message/t.render for messages as data, the Translations registry with fallbacks and
conflicts, a locale preference per principal with the device as default and a live switch, useMessages and
scope.messages, formatTime/formatNumber. The tutorial gains a chapter on languages.
