Logic is shared with the timeline blueprints which also have the same
problem of displaying text on top of a combo colour.
Slightly modified the formula. Seems to yield better results on a
subjective check.
`IdleTracker` in its construction quietly assumed that the clock it
receives from its parent starts ticking from 0 at the point at which it
is passed down. This is not necessarily the case when headless
executions are involved, which means that the initial state of the
tracker could be computed as idle incorrectly.
Resolve by explicitly reading the clock time at the point of
`LoadComplete()`.