## Context
This is the foundation commit for the 'Assign Archetypes to Tasks' feature.
We needed a way to display which agents are assigned to tasks directly on
the graph nodes.
## Decision Process
- User wanted to see agent assignments on DAG nodes
- We discovered that labels (including 'agent:archetype-id' format) weren't
being passed through the WorkflowGraph component
- Added 'labels' and 'archetypes' to GraphNodeData interface
## What Changed
- WorkflowGraph now passes issue.labels to each node's data
- GraphNodeData interface updated to include labels: string[]
- Added archetypes prop for dropdown population
## Test Coverage
- Added graph-node-labels.test.tsx with 4 passing tests
## Beads: beadboard-yo5 (closed)
