Replace the basic canvas bar chart on the web overview with rich worker
cards showing:
- Stacked phase-timing bars (processing/delivery/spawns/overhead)
- Load percentage derived from tick timing active ratio
- Inline sparklines from history (message rate trends)
- Actor count, messages processed, mailbox depth stats
- Color legend for phase identification
Authored by Claude, lovingly guided by Zachery Aaron Shores-Chmielewski