Add GraphQLSchema.FastBuilder, a high-performance schema builder that
avoids full-schema traversals. This initial implementation includes:

- FastBuilder class with constructor accepting code registry builder
  and root types (query, mutation, subscription)
- New private GraphQLSchema constructor for FastBuilder
- ShallowTypeRefCollector stub class for future type reference handling
- Support for adding scalar types via additionalType()
- Automatic addition of built-in directives
- Optional validation support (disabled by default)
- Comprehensive test suite in FastBuilderTest.groovy

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Co-Authored-By: Claude <noreply@anthropic.com>

Implement directive handling in FastBuilder with support for type
references in directive arguments:

- Move ShallowTypeRefCollector to graphql.schema package (for access to
  package-private replaceType methods)
- Implement additionalDirective() with duplicate detection
- Implement ShallowTypeRefCollector.handleDirective() to scan arguments
- Implement type reference resolution for directive arguments
- Support List and NonNull wrapped type references
- Throw AssertException for missing type references
- Add comprehensive tests for directive type reference resolution

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Co-Authored-By: Claude <noreply@anthropic.com>

Enumeration types work with the existing additionalType() implementation.
Add tests to verify:

- Enum types can be added to schema
- Enum type matches standard builder output
- Directive arguments can reference enum types via GraphQLTypeReference

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Co-Authored-By: Claude <noreply@anthropic.com>

Extend ShallowTypeRefCollector to handle GraphQLInputObjectType:

- Scan input object fields for type references
- Implement replaceInputFieldType() for field type resolution
- Support nested input types via type references
- Support List and NonNull wrapped type references in input fields
- Add comprehensive tests for input object type handling

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Co-Authored-By: Claude <noreply@anthropic.com>

Extend ShallowTypeRefCollector to handle applied directives:

- Add scanAppliedDirectives() method for scanning applied directive args
- Scan applied directives on directive container types (enum, scalar, etc.)
- Scan applied directives on input object fields
- Implement replaceAppliedDirectiveArgumentType() for type resolution
- Update FastBuilder.withSchemaAppliedDirective() to scan for type refs
- Add comprehensive tests for applied directive type reference resolution

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Co-Authored-By: Claude <noreply@anthropic.com>

- Extended ShallowTypeRefCollector to handle GraphQLObjectType:
  - Scans field types for type references
  - Scans field arguments for type references
  - Scans applied directives on fields
  - Scans interfaces for type references
- Added resolveOutputType() for output type reference resolution
- Added replaceFieldType() for field type replacement
- Added ObjectInterfaceReplaceTarget wrapper and replaceObjectInterfaces()
- Updated FastBuilder.additionalType() to maintain interface→implementations map
- Added comprehensive tests for object type handling:
  - Field type reference resolution (direct, NonNull, List)
  - Interface type reference resolution
  - Interface→implementations map building
  - Field argument type reference resolution
  - Applied directive on fields
  - Error cases for missing types/interfaces

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Co-Authored-By: Claude <noreply@anthropic.com>

- Extended ShallowTypeRefCollector to handle GraphQLInterfaceType:
  - Scans field types for type references
  - Scans field arguments for type references
  - Scans applied directives on fields
  - Scans extended interfaces for type references
- Added handleInterfaceType() method
- Added InterfaceInterfaceReplaceTarget wrapper class
- Added replaceInterfaceInterfaces() for interface extension resolution
- Updated FastBuilder.additionalType() to wire type resolvers from interfaces
- Added comprehensive tests for interface type handling:
  - Basic interface type addition
  - Field type reference resolution
  - Interface extending interface via type reference
  - Type resolver wiring from interface
  - Field argument type reference resolution
  - Applied directive on interface fields
  - Error cases for missing extended interfaces

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Co-Authored-By: Claude <noreply@anthropic.com>

- Extended ShallowTypeRefCollector to handle GraphQLUnionType:
  - Scans possible types for type references
  - Applied directives already handled by directive container scan
- Added handleUnionType() method
- Added UnionTypesReplaceTarget wrapper class
- Added replaceUnionTypes() for union member type resolution
- Updated FastBuilder.additionalType() to wire type resolvers from unions
- Added comprehensive tests for union type handling:
  - Basic union type addition
  - Union member type reference resolution
  - Type resolver wiring from union
  - Error cases for missing member types
  - Applied directive on union types

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Co-Authored-By: Claude <noreply@anthropic.com>

- Fixed additionalTypes not being set in FastBuilder path:
  - Added additionalTypes parameter to FastBuilder private constructor
  - Added buildAdditionalTypes() method to compute additionalTypes from typeMap
  - Validation now properly traverses all types in the schema
- Added comprehensive tests for validation and edge cases:
  - withValidation(false) skips validation
  - withValidation(true) runs validation and catches errors
  - Circular type reference resolution
  - Deeply nested type reference resolution (NonNull + List + NonNull)
  - Complex schema with interfaces, unions, input types
  - Null handling for types/directives
  - Built-in directives are added automatically

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Co-Authored-By: Claude <noreply@anthropic.com>

Add BuildSchemaBenchmark to measure schema construction performance in isolation
from SDL parsing. This benchmark compares standard SchemaGenerator against
FastSchemaGenerator using the large-schema-4.graphqls test schema (~18,800 types).

Changes:
- Add FastSchemaGenerator that uses FastBuilder for optimized schema
  construction from pre-parsed TypeDefinitionRegistry
- Add BuildSchemaBenchmark.java with side-by-side comparison of standard vs fast
  schema generation, parsing SDL once in @setup to isolate build performance
- Add jmhProfilers gradle property support for GC profiling (e.g., -PjmhProfilers="gc")
- Add FastSchemaGeneratorTest to verify equivalence with standard SchemaGenerator

Usage:
  ./gradlew jmh -PjmhInclude=".*BuildSchemaBenchmark.*"
  ./gradlew jmh -PjmhInclude=".*BuildSchemaBenchmark.*" -PjmhProfilers="gc"