appEvents double-logging inflates error-cluster counts ~2x

A serverError and its client-boundary companion clientError (empty errorStack) both write rows for ONE incident, ~2x-inflating error-cluster counts + risking double-page. Surfaced by PLUTO-188 (the /informes cluster was 2x-inflated this way). Investigate the logger/error-boundary write path (instrumentation.ts onRequestError + client error.tsx/global-error.tsx capture) — dedup or suppress the empty-stack companion so one incident = one row. Low-pri hardening.