Investigate main-thread freezes / slow pages with a real CPU profile instead of guessing. Use when a page locks up, the sidebar/cards go unresponsive, requests hang pending, a 'freeze' or 'jank' is reported, or you need to prove a perf fix worked (before/after). Drives a real browser via agent-browser, captures a Chrome DevTools profile, and parses it for the dominant hot frame — separating real app cost from profiler/dev-mode artifacts.
