feat(schema/graph-schemas): define TaskGraphNodeAttributes, TaskGraphEdgeAttributes, and SerializedGraph generic

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.

src/schema/graph.ts

@@ -1 +1,89 @@
-// TaskGraphNodeAttributes, TaskGraphEdgeAttributes, SerializedGraph schemas
+import { Type, type Static, type TSchema } from "@alkdev/typebox";
+import {
+  TaskScopeEnum,
+  TaskRiskEnum,
+  TaskImpactEnum,
+  TaskLevelEnum,
+  TaskPriorityEnum,
+  TaskStatusEnum,
+} from "./enums.js";
+
+// --- TaskGraphNodeAttributes ---
+
+/** Node attributes stored on the graphology graph. Carries only analysis-relevant metadata. */
+export const TaskGraphNodeAttributes = Type.Object({
+  name: Type.String(),
+  scope: Type.Optional(TaskScopeEnum),
+  risk: Type.Optional(TaskRiskEnum),
+  impact: Type.Optional(TaskImpactEnum),
+  level: Type.Optional(TaskLevelEnum),
+  priority: Type.Optional(TaskPriorityEnum),
+  status: Type.Optional(TaskStatusEnum),
+});
+/** Inferred type for {@link TaskGraphNodeAttributes} schema. */
+export type TaskGraphNodeAttributes = Static<typeof TaskGraphNodeAttributes>;
+
+// --- TaskGraphNodeAttributesUpdate ---
+
+/** All fields optional for partial-update operations. */
+export const TaskGraphNodeAttributesUpdate = Type.Partial(TaskGraphNodeAttributes);
+/** Inferred type for {@link TaskGraphNodeAttributesUpdate} schema. */
+export type TaskGraphNodeAttributesUpdate = Static<typeof TaskGraphNodeAttributesUpdate>;
+
+// --- TaskGraphEdgeAttributes ---
+
+/** Edge attributes stored on the graphology graph. */
+export const TaskGraphEdgeAttributes = Type.Object({
+  qualityRetention: Type.Optional(Type.Number()),
+});
+/** Inferred type for {@link TaskGraphEdgeAttributes} schema. */
+export type TaskGraphEdgeAttributes = Static<typeof TaskGraphEdgeAttributes>;
+
+// --- SerializedGraph generic factory ---
+
+/**
+ * Generic schema factory for the graphology native JSON format.
+ * Parameterized with node attribute, edge attribute, and graph attribute schemas.
+ *
+ * @param NodeAttrs - Schema for node attributes
+ * @param EdgeAttrs - Schema for edge attributes
+ * @param GraphAttrs - Schema for graph-level attributes
+ */
+export const SerializedGraph = <N extends TSchema, E extends TSchema, G extends TSchema>(
+  NodeAttrs: N,
+  EdgeAttrs: E,
+  GraphAttrs: G,
+) =>
+  Type.Object({
+    attributes: GraphAttrs,
+    options: Type.Object({
+      type: Type.Literal("directed"),
+      multi: Type.Literal(false),
+      allowSelfLoops: Type.Literal(false),
+    }),
+    nodes: Type.Array(
+      Type.Object({
+        key: Type.String(),
+        attributes: NodeAttrs,
+      }),
+    ),
+    edges: Type.Array(
+      Type.Object({
+        key: Type.String(),
+        source: Type.String(),
+        target: Type.String(),
+        attributes: EdgeAttrs,
+      }),
+    ),
+  });
+
+// --- TaskGraphSerialized ---
+
+/** Serialized task graph following graphology native JSON format. */
+export const TaskGraphSerialized = SerializedGraph(
+  TaskGraphNodeAttributes,
+  TaskGraphEdgeAttributes,
+  Type.Object({}),
+);
+/** Inferred type for {@link TaskGraphSerialized} schema. */
+export type TaskGraphSerialized = Static<typeof TaskGraphSerialized>;