lib/posthog/events.ts was importing from components/assistant-ui/...,
creating an inverted dependency layer (lib → components).
Move ConnectorTelemetryMeta type, CONNECTOR_TELEMETRY_REGISTRY,
getConnectorTelemetryMeta, and getReauthEndpoint into the new
lib/connector-telemetry.ts module so that lib/ no longer depends upward
into the UI tree.
connector-constants.ts now re-exports from the new module for
backward compatibility.
Fixes#1375
