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/host-reactive.md

@@ -0,0 +1,50 @@
+---
+id: host/reactive
+name: Implement ReactiveHostConfig — render ujsx template to reactive execution engine
+status: pending
+depends_on:
+  - component/operation
+  - component/sequential
+  - component/parallel
+  - component/conditional
+  - component/map
+  - reactive/workflow-root
+  - reactive/node-status
+  - schema/edge-attrs
+scope: broad
+risk: critical
+impact: phase
+level: implementation
+---
+
+## Description
+
+Implement the `ReactiveHostConfig` that renders a ujsx workflow template into a reactive execution engine with signal-backed `NodeStatus` tracking, computed preconditions, and failure propagation. This is the runtime execution rendering path.
+
+## Acceptance Criteria
+
+- [ ] `src/host/reactive.ts` exports `ReactiveHostConfig` implementing ujsx `HostConfig<WorkflowTag, WorkflowNode, ReactiveContext>`
+- [ ] `WorkflowNode`: `{ key, type, status: Signal<NodeStatus>, preconditions: Computed<boolean>, blockedByFailure: Computed<boolean>, operationId?, output?: Signal<unknown>, children: WorkflowNode[] }`
+- [ ] `ReactiveContext`: `{ operationRegistry, nodes: Map, statusSignals: Map, preconditions: Map, blockedByFailure: Map, resultProjection: EventLogProjection, parentMap, siblingMap, results: Map }`
+- [ ] `createInstance("operation", props, ctx)`: creates `WorkflowNode` with status signal from `ReactiveContext`, registers in context maps
+- [ ] `createInstance` for structural containers: creates WorkflowNode tracking children but no graph node
+- [ ] Prerequisite computation: Sequential child → previous sibling completed/skipped; Parallel child → parent's preconditions met; Conditional child → condition evaluates to true
+- [ ] Status propagation: effects on `preconditions` and `blockedByFailure` drive state transitions
+- [ ] `removeChild`: removes parent-child dependency, preconditions/blockedByFailure auto-re-evaluate (reactive)
+- [ ] `removeChildFromHost`: disposes node's signal references from context maps
+- [ ] Re-exported from `src/host/index.ts`
+- [ ] Integration tests: render template → assert signal initial states, transition predecessor → assert dependent precondition updates, failure propagation, Conditional as error boundary
+
+## References
+
+- docs/architecture/host-configs.md — ReactiveHostConfig full specification, WorkflowNode, ReactiveContext
+- docs/architecture/reactive-execution.md — signal-backed execution model, precondition computation, status propagation
+- docs/architecture/workflow-templates.md — template→reactive execution conversion
+
+## Notes
+
+> To be filled by implementation agent
+
+## Summary
+
+> To be filled on completion