- RoleDefinition.extractMode: "single" | "react"
- reactExtract: multi-turn LLM with cas_get tool for DAG traversal
- Max 10 tool-call rounds, schema validation on final output
- create-workflow routes to reactExtract when extractMode is "react"
- All existing roles set to "single" (no behavior change)
- 162 tests passing
Fixes#44
