Schedule health

Every task's health is derived, never manually maintained. From its status, whether it is past its end date, and whether an unfinished dependency blocks it, the widget computes one of:

• On track — proceeding as planned.
• Overdue — past its end date and not done (‼️ corner flag).
• Blocked — waiting on an unfinished dependency (🚧 corner flag).
• Done — finished, and dimmed on the canvas.

Because it is computed at render time, the plan is always honest — there's no stale status to keep up to date.