Implements graph attribute schemas and the SerializedGraph generic factory
parameterized with <N, E, G> following the graphology JSON format.
- TaskGraphNodeAttributes: name + optional categorical enums (scope, risk,
impact, level, priority, status) — analysis-relevant metadata only
- TaskGraphNodeAttributesUpdate: Type.Partial(TaskGraphNodeAttributes)
- TaskGraphEdgeAttributes: optional qualityRetention number
- SerializedGraph<N, E, G>: generic factory for graphology JSON format
- TaskGraphSerialized: concrete instantiation with empty graph attributes
- No schema version field per spec
35 new tests covering validation, rejection, and compile-time type safety.
- Add TaskInput schema with all fields per architecture (id, name, dependsOn,
categorical fields as Optional(Nullable(...)), metadata fields)
- Add DependencyEdge schema with from, to, qualityRetention fields
- Re-export Nullable helper from task.ts for convenience
- Add type aliases: TaskInput, DependencyEdge via Static<typeof>
- Add 49 tests covering validation, nullable fields, edge cases, type correctness
