decompose architecture into 38 atomic tasks across 12 parallel generations

Decompose the reviewed architecture specs into taskgraph-managed tasks:
- 2 setup tasks (project init, test infrastructure)
- 4 schema tasks (enums, node attrs, edge attrs, graph schemas)
- 1 error hierarchy task
- 6 graph tasks (FlowGraph class, 3 construction paths, queries, validation)
- 5 analysis tasks (type-compat, build-type-edges, ordering, template-validation, defaults)
- 5 component tasks (Operation, Sequential, Parallel, Conditional, Map)
- 2 host config tasks (GraphologyHostConfig, ReactiveHostConfig)
- 4 reactive tasks (WorkflowRoot, node-status, max-concurrency, retry-semantics)
- 3 review tasks (foundation, reactive-and-hosts, complete-library)
- 5 meta cluster tasks (schema, graph, component, reactive, analysis layers)
- 1 API exports task

Validated with taskgraph: zero cycles, 38 tasks, 12 parallel generations.
Critical path: 12 tasks through reactive execution layer.

tasks/setup-test-infrastructure.md

@@ -0,0 +1,39 @@
+---
+id: setup/test-infrastructure
+name: Set up vitest test infrastructure with fixtures, helpers, and reactive test patterns
+status: pending
+depends_on:
+  - setup/project-init
+scope: narrow
+risk: low
+impact: component
+level: implementation
+---
+
+## Description
+
+Create the test infrastructure that all downstream test files will depend on: shared fixtures, helper functions for graph construction, and the reactive test pattern (create root → transition → assert → dispose). This ensures consistent test setup across all modules.
+
+Per [build-distribution.md](../docs/architecture/build-distribution.md) testing strategy section.
+
+## Acceptance Criteria
+
+- [ ] `test/helpers/` directory with shared test utilities
+- [ ] `test/helpers/graph-factory.ts` — helpers to build test operation graphs and call graphs with known structures
+- [ ] `test/helpers/reactive.ts` — helper to create `WorkflowReactiveRoot` instances for testing: setup → transition → assert → dispose pattern
+- [ ] `test/helpers/schemas.ts` — sample TypeBox schemas for testing `typeCompat()` (compatible pairs, incompatible pairs, unknown schemas)
+- [ ] All helpers are importable from `test/helpers/`
+- [ ] `vitest.config.ts` includes `test/helpers/` in setup or alias configuration
+
+## References
+
+- docs/architecture/build-distribution.md — testing strategy, reactive test patterns
+- docs/architecture/reactive-execution.md — WorkflowReactiveRoot lifecycle (setup → assert → dispose)
+
+## Notes
+
+> To be filled by implementation agent
+
+## Summary
+
+> To be filled on completion