feat(schema): export schema types, GetSchema<T>, ValidateReturn, and rule types

[SrHenry]

Summary

• Extract 11 inline schema type definitions from builder files into dedicated type files under src/validators/schema/types/ (BooleanSchema, NullSchema, UndefinedSchema, SymbolSchema, AnySchema, PrimitiveSchema, EnumSchema, ObjectSchema, TupleSchema, UnionSchema, IntersectionSchema)
• Add GetSchema<T> recursive type helper that maps TypeScript types to their corresponding FluentSchema result types
• Re-export all new schema types, ValidateReturn, and rule types (Custom, CustomFactory, Rule, CreateRuleArgs) from the types hub
• Replace export * from ./v3/index.ts wildcard with explicit allowlist to prevent internal V3 composition types from leaking into the public API
• Replace export * from ./types/index.ts wildcard in rules barrel with explicit type allowlist to prevent CUSTOM_RULE_BRAND (runtime symbol) and RuleStruct (internal dispatch type) from reaching the public API
• Remove Optionalize<T>, GetSchemaStruct<T>, and RuleStruct<Rule> from public exports (internal-only, no external consumers)
• Fix GetSchema edge cases: any guard, unknown/void/never branches, Record detection for all key types

Exports now available from @srhenry/type-utils

Type	Description
GetSchema<T>	Maps TS type → FluentSchema result type
ValidateReturn<T>	Return type of schema validation
BooleanSchema, NullSchema, UndefinedSchema, SymbolSchema, AnySchema, PrimitiveSchema	Simple schema builder types
EnumSchema, ObjectSchema, TupleSchema, UnionSchema, IntersectionSchema	Complex schema builder types
TupleSchemaEntry, UnionSchemaEntry, IntersectionSchemaEntry	Entry types for composite schemas
GetUnionEntryTypes, GetIntersectionEntryTypes	Helper types for union/intersection entry unwrapping
Custom, CustomFactory, Rule, CreateRuleArgs	Rule types
V1, V2, V3	Historical version namespaces
BaseStruct, TUnion, TIntersection, TypeGuardTupleUnwrap	V3 flat exports (explicit allowlist)
GenericStruct, ObjectStruct, Struct, StructType	Top-level V3 aliases (backward compat)

Key change: V3 wildcard → explicit allowlist

The barrel file src/validators/schema/types/index.ts previously used export * from './v3/index.ts', which re-exported every type inside the V3 namespace flat — including ~25 internal composition types that consumers should never import directly:

RequiredPartialStruct, OptionalPartialStruct, RequirefyStruct, OptionalizeStruct, WithRulesStruct, MapToStructs, ExactExtends, IsExactExtension, ObjectTree, ClassInstanceRef, ArrayEntries, RecordMetadata, TupleMetadata, TupleToTypeGuardMap, TupleToStructMap, AsPrimitiveStruct, FromUnionStruct, FromIntersectionStruct, FromRecordStruct, FromClassInstanceStruct, FromTupleStruct

These types are still accessible to internal consumers via the V3 namespace (e.g. V3.RequiredPartialStruct), but they are no longer re-exported as bare names from the barrel. Only the 4 top-level flat exports from v3/index.ts are explicitly allowed through: BaseStruct, TUnion, TIntersection, TypeGuardTupleUnwrap.

Note: The V3 concrete struct types (V3.StringStruct, V3.NumberStruct, etc.) were never available as bare flat imports — they were always inside the V3 namespace on the original developer branch. This PR does not change that.

Key change: Rules barrel wildcard → explicit allowlist

Similarly, src/validators/rules/index.ts previously used export * from ./types/index.ts, which re-exported CUSTOM_RULE_BRAND (a runtime unique symbol used internally for type branding) and RuleStruct<Rule> (an internal dispatch type). These are now excluded from the public API by replacing the wildcard with an explicit type allowlist. Internal consumers still import these directly from ./types/index.ts.

Key change: GetSchema edge cases

• GetSchema<any>: Previously mis-mapped to FluentSchema<string, StringSchemaRules> because any distributes through conditionals. Now uses the 0 extends (1 & T) guard pattern to detect any early, correctly resolving to FluentSchema<any>.
• GetSchema<unknown>: Previously returned never because unknown fails all conditional branches. Now has an explicit branch mapping to FluentSchema<any>.
• GetSchema<void>: Added explicit branch mapping to FluentSchema<any>. Previously fell through to never.
• GetSchema<never>: Explicitly returns never — intentional, since never inputs should produce never outputs.
• GetSchema<Record<K, V>>: Previously used PropertyKey extends keyof T which never matched any Record type because symbol doesn't extend string or number. All Records silently fell through to the "specific object" branch, losing RecordSchemaRules (including .nonEmpty()). Now uses per-key-type checks: string extends keyof T, number extends keyof T, symbol extends keyof T — correctly detecting Records with any broad key type.
• Unreachable never fallbacks: The broad string/number detection branches ([string] extends [T], [number] extends [T]) have documented never fallbacks for cases where [K] extends [T] is true but T extends K is false. These are unreachable because the only such types are any and unknown, both caught earlier, but the fallbacks are safety nets documented for future maintainers.

Test Plan

• yarn tsc -p tsconfig.json --noEmit — all type assertions pass
• yarn tsc -p tsconfig.esm.json --noEmit — ESM typecheck passes
• yarn tsc -p tsconfig.cjs.json --noEmit — CJS typecheck passes
• yarn test — 382 passed, 1 skipped
• yarn build — ESM + CJS outputs generated
• yarn check:fix — lint + format clean
• yarn circular-dependencies — 0 circular deps
• All new types importable from @srhenry/type-utils entry
• GetSchema type-level assertions compile correctly (all cases including any, unknown, void, never, Record<string,V>, Record<number,V>, Record<symbol,V>, function, Date)
• Strict Record assertions verify RecordSchemaRules is present (not {}), ensuring .nonEmpty() method is available
• Internal V3 types no longer leak as flat exports
• CUSTOM_RULE_BRAND and RuleStruct no longer in public API