Project · Plans: a roadmap, a burndown, milestones, workload

Roadmap lays initiatives across months in lanes: each a bar from its
first day through its last, filled as far as it has come, under the
months' names and a line at today; hover a bar for its dates. Bars sit
at fractions of the span, so nothing is measured, and a strip too
narrow for its months scrolls sideways at a least width per month.
GanttChart and TimelineView are the charts GanttChart.

BurndownChart lives with the charts, on their scales, labels, tiles
and paint: the ideal line from the scope down to nothing, what was left
at each day's end so far, and a line at today; hover a day to read it.

MilestoneProgress shows a milestone's issues done as a bar and a count,
when it is due, and whether it keeps pace: on track, at risk when the
work trails the time gone by more than a tenth, late past its day, or
done. WorkloadView sets each person's points against what they can
take, the bar turning red past it, in columns that line up.

src/theme/project.rs

@@ -7,12 +7,15 @@ use super::{Theme, tokens::px_to_rems};
 pub struct ProjectSizes {
     /// A board's column, wide.
     pub column: Rems,
+    /// A roadmap's month at least, wide.
+    pub month: Rems,
 }
 
 impl Theme {
     pub fn project(&self) -> ProjectSizes {
         ProjectSizes {
             column: px_to_rems(272.0),
+            month: px_to_rems(72.0),
         }
     }
 }