<bmx-pert-chart>
The plan as a network.
Each box carries its critical-path arithmetic: earliest start, length and earliest finish
across the top; latest start, float and latest finish across the bottom. The chart reads the same
tasks and links as bmx-gantt and bmx-task-board, so the three
can show one plan side by side.
Read in order, not by lines. Each box says what it follows and what it leads to. Tab in once;
→ goes to the next piece of work, ← to the one before, ↑ and
↓ along a column. Drag the background to pan, and Ctrl with the wheel to zoom.
Every property, event and method: https://docs.binarymission.co.uk/webcomponents/bmx/bmx-pert-chart.html