v0.6.0

New diagram types

• Gantt chart (gantt): horizontal bar chart with sections, task tags (done/active/crit/milestone), after dependencies, duration syntax, auto-chaining, vertical markers, today marker
• Architecture diagram (architecture-beta): service/group/junction layout with L/R/T/B direction hints for 2D grid positioning, icon prefixes, invisible junction elimination

18 diagram types now supported.