The one-slot context model — time and branches from a single field
When two contexts in the selected chain disagree, the later one wins (later = further from root).
That single rule is the whole abstraction:
- chain + later-wins → time
- branch + later-wins → scenarios
- unordered + explicit priority → overlays (draft over approved)
- unordered + keep-both → perspectives (Design vs Eng, side by side)
No clock, no fold, no slider, no as_of baked into the graph. Just contexts, an after link, and
later-wins. See context_demo.py for the birdhouse running both a time projection and a branch.