Add naming pipelines, buildTypeGraph, and printMutatedType to mutation engine

[swatkatz]

Summary

• Moves all naming transforms into the mutation engine — after mutation, type.name is the final GraphQL identifier
• Adds buildTypeGraph for packaging mutated types into a self-contained TypeGraph (ref: Timothee's TypeGraph concept)
• Adds printMutatedType for stringifying mutation output as GraphQL type strings
• Splits monolithic test file into 9 focused files

New modules

Module	Purpose
src/lib/naming.ts	Ordered naming pipelines (strip namespace → sanitize → case convert → suffixes)
src/lib/template-composition.ts	Recursive template name composition using TemplatedType
src/mutation-engine/type-graph.ts	buildTypeGraph + TypeGraph interface (inter-stage/inter-emitter contract)
src/mutation-engine/print-type.ts	printMutatedType — renders mutation output as GraphQL type string

Naming pipeline design

Transforms are declared as ordered lists — order enforced by position:

const typeNamePipeline = [stripNamespace, sanitizeForGraphQL, toPascalCase, applyInterfaceSuffix, applyInputSuffix];
const fieldNamePipeline = [sanitizeForGraphQL, toCamelCase];
const enumMemberPipeline = [sanitizeForGraphQL, toConstantCase];

Context-dependent suffixes (Input, Interface) are pipeline steps that no-op when their flag is false.

Test plan

• 189 tests pass (18 test files)
• Build compiles cleanly (tsc -p .)
• Type check clean (no errors in new/modified files)
• Prettier formatted
• Naming pipeline unit tests (19 tests)
• Template composition tests with recursive nesting (7 tests)
• buildTypeGraph tests including stage chaining (8 tests)
• printMutatedType tests covering all nullability combinations (10 tests)
• Mutation integration tests verifying pipelines are wired (8 tests)
• Union oneOf naming consistency (snake_case → PascalCase + camelCase)

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