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/graph-flowgraph-class.md

@@ -0,0 +1,58 @@
+---
+id: graph/flowgraph-class
+name: Implement FlowGraph class skeleton wrapping graphology DirectedGraph
+status: pending
+depends_on:
+  - schema/enums
+  - schema/node-attrs
+  - schema/edge-attrs
+  - schema/graph-schemas
+  - error/hierarchy
+  - setup/project-init
+scope: moderate
+risk: medium
+impact: phase
+level: implementation
+---
+
+## Description
+
+Create the `FlowGraph` class that wraps a graphology `DirectedGraph` and enforces DAG invariants. This is the core data class. At this stage, implement the constructor, generic type parameters, the `_graph` instance, the `graph` getter, `FlowGraphOptions`, and the `_edgeKey()` helper. Construction factory methods come in dependent tasks.
+
+## Acceptance Criteria
+
+- [ ] `src/graph/construction.ts` exports `FlowGraph` class (or `src/graph/index.ts` if preferred, matching source structure)
+- [ ] Class has type parameters: `NodeAttrs extends TSchema`, `EdgeAttrs extends TSchema`
+- [ ] Constructor creates internal `graphology.DirectedGraph` with options `{ type: "directed", multi: false, allowSelfLoops: false }`
+- [ ] `FlowGraphOptions` interface: `type?: "directed"`, `multi?: false`, `allowSelfLoops?: false`
+- [ ] `get graph(): DirectedGraph` returns the underlying graphology instance
+- [ ] `_edgeKey(source, target): string` produces deterministic keys `${source}->${target}`
+- [ ] `addNode(key, attrs)` — adds node, throws `DuplicateNodeError` on duplicate
+- [ ] `removeNode(key)` — removes node and edges, throws `NodeNotFoundError` if missing
+- [ ] `updateNode(key, attrs)` — partial merge of attributes, throws `NodeNotFoundError` if missing
+- [ ] `hasNode(key): boolean`
+- [ ] `getNodeAttributes(key): NodeAttrs` — throws `NodeNotFoundError` if missing
+- [ ] `addEdge(source, target, attrs?)` — throws `NodeNotFoundError` for missing endpoints, `CycleError` if edge creates cycle, `DuplicateEdgeError` if edge exists
+- [ ] `removeEdge(source, target)` — no-op if edge doesn't exist
+- [ ] `hasEdge(source, target): boolean`
+- [ ] `getEdgeAttributes(source, target): EdgeAttrs` — throws if edge doesn't exist
+- [ ] `nodes(): string[]`, `edges(): string[]`, `order: number`, `size: number`
+- [ ] `forEachNode(callback)`, `forEachEdge(callback)`
+- [ ] `predecessors(nodeId)`, `successors(nodeId)` delegating to `graph.inNeighbors`/`graph.outNeighbors`
+- [ ] Static construction methods (`fromSpecs`, `fromCallEvents`, `fromJSON`) are stubs (throw "not implemented")
+- [ ] Re-exported from `src/graph/index.ts` and `src/index.ts`
+- [ ] Unit tests: constructor, node operations, edge operations, cycle detection on addEdge
+
+## References
+
+- docs/architecture/flowgraph-api.md — FlowGraph class full API surface, delegation model
+- docs/architecture/schema.md — edge key convention
+- docs/architecture/error-handling.md — throwing contract for mutations
+
+## Notes
+
+> To be filled by implementation agent
+
+## Summary
+
+> To be filled on completion