Render scheduler trace as digital signals

[espmaniac]

What changed

• replace glowing execution bars with logic-analyzer-style task signals
• keep the trace at LOW only while a task is idle
• render every scheduler slice as a sharp LOW → HIGH → LOW transition
• make each HIGH plateau follow the measured slice duration
• render every task row as one continuous signal, without a LOW line underneath HIGH
• retain rolling-left motion, task colors, execution share, and hover details
• widen only sub-pixel pulses enough to remain visible and merge them when their rendered widths touch

Why

The first timeline version showed activity clearly, but it looked like isolated markers. A digital waveform makes the task state over time immediately readable: LOW is idle and HIGH is running.

Validation

• node --check main.js
• git diff --check
• waveform geometry smoke test for LOW gaps, HIGH plateaus, overlapping sub-pixel pulses, and left-window clipping
• exact public commit preview reached Runtime: OK and rendered the new timeline copy
• GitHub Actions Build browser runtime run #63 completed successfully