Datadog Browser RUM instrumentation

Instrument only the browser application in scope. Do not add Datadog APM, tracing, LLM Observability, Logs, source-map upload, user identification, Vercel metadata, Shopify, Salesforce, or unrelated Datadog products.

Use normal file inspection, editing, and command tools for every step except optional RUM application creation. Use only CreateRumApplication for that operation, as described in references/common-credentials.md; never invent Datadog tool names.