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/meta-reactive-layer.md

@@ -0,0 +1,38 @@
+---
+id: meta/reactive-layer
+name: Complete reactive execution layer — WorkflowRoot, node-status, maxConcurrency, retries
+status: pending
+depends_on:
+  - reactive/workflow-root
+  - reactive/node-status
+  - reactive/max-concurrency
+  - reactive/retry-semantics
+scope: broad
+risk: high
+impact: phase
+level: planning
+---
+
+## Description
+
+Meta task that clusters all reactive execution tasks. Once complete, the reactive layer provides signal-backed execution with automatic precondition resolution, failure propagation, and event-log-driven state management.
+
+## Acceptance Criteria
+
+- [ ] All reactive tasks completed
+- [ ] WorkflowReactiveRoot implements EventLogProjection correctly
+- [ ] Preconditions drive automatic state transitions
+- [ ] Failure follows dependency edges, not structural scope
+- [ ] dispose() prevents signal leaks
+
+## References
+
+- docs/architecture/reactive-execution.md
+
+## Notes
+
+> To be filled by implementation agent
+
+## Summary
+
+> To be filled on completion