Pulls the CPU chart's SVG-drawing logic into a parameterized
renderTimeSeriesChart(elId, pts, opts) helper (yDomain, colorFor,
clipId, unitSuffix), keeping renderCpuChart's signature and behavior
unchanged. Task 5 will reuse this for the RTT chart.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01DEimzMv4Q5EjFg3hoiZ69T