Hotfix prod deploy — 250MB serverless function size limit (Nick report)

Production deploys broken since PR #258 merge at 2026-05-21 15:33 UTC. Root cause: @texturehq/edges 1.30.3→1.33.2 bump pulled mapbox/visx/tiptap/ace/framer-motion etc into output file traces, ballooning every API serverless function past 250MB. Fix lived on meridian/edges-migration (PR #257) but never landed — that PR is blocked behind larger edges-tokens migration, and PR #258 merged on top of the edges bump without the trace excludes fix. Hotfix PR #259 cherry-picks ONLY the outputFileTracingExcludes config from PR #257 onto current main as next.config.mjs change. Branch: meridian/hotfix-vercel-250mb-deploy. Next: monitor CI, verify Vercel preview build passes the bundle size check, merge when green, confirm prod deploy succeeds, reply to Nick in thread C0AGCGPAGQZ/1779378071.022259.