Main-thread CPU time per page (energy beyond bytes)

[mgifford]

Size: M. CDP Performance.getMetrics (TaskDuration, ScriptDuration) per canonical scan → history.json. Bytes are a proxy; CPU time catches JS-heavy energy regressions with identical page weight. Feeds the Default Admin payload-budget issue.

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Scoped in TOOLING-ROADMAP.md — sized to complete in one AI session. Drafted with AI assistance (Claude Code); no external code copied.