feat(api/public-exports): wire up selective public API surface in src/index.ts

Replace wildcard  barrel with selective named re-exports,
ensuring no internal implementation details (TaskGraphInner, Nullable,
SerializedGraph, standalone mutation/query/validation functions,
computeEffectiveP, splitFrontmatter) leak through the public API.

All 590 tests pass, TypeScript declarations compile cleanly.

src/index.ts

@@ -1,8 +1,109 @@
 // @alkdev/taskgraph — Public API surface
-// Re-exports from all submodules
+//
+// This is the main entry point for consumers. Everything they need should be
+// importable from `@alkdev/taskgraph`. Internal implementation details (types
+// and functions that operate on the raw graphology instance) are intentionally
+// NOT re-exported here to maintain a clean public API boundary.
 
-export * from './schema/index.js';
-export * from './graph/index.js';
-export * from './analysis/index.js';
-export * from './frontmatter/index.js';
-export * from './error/index.js';
+// ---------------------------------------------------------------------------
+// TaskGraph class (the primary data structure)
+// ---------------------------------------------------------------------------
+
+export { TaskGraph } from './graph/construction.js';
+
+// ---------------------------------------------------------------------------
+// Analysis functions (standalone, composable)
+// ---------------------------------------------------------------------------
+
+// Graph analysis
+export { parallelGroups } from './analysis/parallel-groups.js';
+export { criticalPath, weightedCriticalPath } from './analysis/critical-path.js';
+export { bottlenecks } from './analysis/bottleneck.js';
+export type { BottleneckResult } from './analysis/bottleneck.js';
+
+// Cost-benefit analysis
+export { riskPath, riskDistribution } from './analysis/risk.js';
+export { calculateTaskEv, workflowCost } from './analysis/cost-benefit.js';
+export { shouldDecomposeTask } from './analysis/decompose.js';
+
+// Categorical numeric methods
+export {
+  scopeCostEstimate,
+  scopeTokenEstimate,
+  riskSuccessProbability,
+  riskWeight,
+  impactWeight,
+  resolveDefaults,
+} from './analysis/defaults.js';
+
+// ---------------------------------------------------------------------------
+// Frontmatter functions
+// ---------------------------------------------------------------------------
+
+export { parseFrontmatter } from './frontmatter/parse.js';
+export { serializeFrontmatter } from './frontmatter/serialize.js';
+export { parseTaskFile, parseTaskDirectory } from './frontmatter/file-io.js';
+
+// ---------------------------------------------------------------------------
+// Schemas and types
+// ---------------------------------------------------------------------------
+
+// Enum schemas + types (const+type pairs with same name: export by value, TS includes type)
+export {
+  TaskScopeEnum,
+  TaskRiskEnum,
+  TaskImpactEnum,
+  TaskLevelEnum,
+  TaskPriorityEnum,
+  TaskStatusEnum,
+} from './schema/enums.js';
+
+export type {
+  TaskScope,
+  TaskRisk,
+  TaskImpact,
+  TaskLevel,
+  TaskPriority,
+  TaskStatus,
+} from './schema/enums.js';
+
+// Input schemas + types
+export { TaskInput, DependencyEdge } from './schema/task.js';
+
+// Graph schemas + types (exclude SerializedGraph generic factory and TaskGraphNodeAttributesUpdate)
+export {
+  TaskGraphNodeAttributes,
+  TaskGraphEdgeAttributes,
+  TaskGraphSerialized,
+} from './schema/graph.js';
+
+// Result schemas + types
+export {
+  RiskPathResult,
+  DecomposeResult,
+  WorkflowCostOptions,
+  WorkflowCostResult,
+  EvConfig,
+  EvResult,
+  RiskDistributionResult,
+  ResolvedTaskAttributes,
+} from './schema/results.js';
+
+// ---------------------------------------------------------------------------
+// Error classes + validation error types
+// ---------------------------------------------------------------------------
+
+export {
+  TaskgraphError,
+  TaskNotFoundError,
+  CircularDependencyError,
+  InvalidInputError,
+  DuplicateNodeError,
+  DuplicateEdgeError,
+} from './error/index.js';
+
+export type {
+  ValidationError,
+  GraphValidationError,
+  AnyValidationError,
+} from './error/index.js';

src/schema/index.ts

@@ -1,4 +1,7 @@
-// Schema submodule — re-exports
+// Schema submodule — public re-exports
+//
+// Excludes: Nullable (internal TypeBox helper), SerializedGraph (generic factory),
+// TaskGraphNodeAttributesUpdate (internal use for update operations)
 
 export * from './enums.js';
 export * from './task.js';

src/schema/task.ts

@@ -9,9 +9,6 @@ import {
   TaskPriorityEnum,
 } from "./enums.js";
 
-// Re-export Nullable for convenience (originally defined in enums.ts)
-export { Nullable } from "./enums.js";
-
 // --- Input Schemas ---
 
 /**

test/schema.test.ts

@@ -369,14 +369,8 @@ describe('Type alias correctness — TaskInput and DependencyEdge (compile-time)
   });
 });
 
-// Re-export Nullable from task.ts to verify the re-export works
-import { Nullable as NullableFromTask } from '../src/schema/task.js';
-
-describe('Nullable re-export from task.ts', () => {
-  it('is the same function as from enums.ts', () => {
-    expect(NullableFromTask).toBe(Nullable);
-  });
-});
+// Nullable is no longer re-exported from task.ts — it's an internal helper
+// and excluded from the public API surface per src/index.ts
 
 // Intentionally import type aliases to verify they exist at compile time
 type TaskScope = import('../src/schema/enums.js').TaskScope;