feat: generate tuple type for fixed-length arrays (min equals max)

[2wheeh]

Description

When an array schema has minItems === maxItems, generate a tuple type instead of T[].

// Before
FromSchema<{ type: "array"; items: { type: "string" }; minItems: 2; maxItems: 2 }>
// => string[]

// After
// => [string, string]

This PR only handles the equal case (minItems === maxItems).

It seems Range support (minItems !== maxItems → union of tuple lengths) is easily possible by reusing the existing ApplyMinMax pipeline with Repeat, but left out intentionally due to:

• Performance concerns with large ranges (deep type-level recursion)
• Need a disscussion for a code size guard (similar to openapi-typescript's estimateCodeSize < 30)

Changes

• Added Repeat<T, N> type utility that builds a fixed-length tuple of repeated type
• Added ParseArraySchema in array.ts to check minItems === maxItems and produce M.$Tuple via Repeat
• Falls back to M.$Array (existing behavior) for all other cases

Breaking change

This is technically a narrowing change: string[] → [string, string]. Code that assigns a general T[] to a FromSchema type with fixed-length constraints may break. The type is now more correct but stricter — may warrant a minor version bump.