feat(pagination): add generic paginateArray helper to horizonPaginator (#618)

[s6pa1rta3n-lab]

Overview

Implements a generic paginateArray helper in src/horizonPaginator.ts for paginating in-memory arrays (such as local arrays of invoices or payments) with 1-indexed pagination, range boundary checks, and SdkError error handling.

Related Issue

Closes #618

Changes

• [MODIFY] src/horizonPaginator.ts
  • Implemented and exported generic paginateArray<T>(items: T[], opts: { page: number; pageSize: number }) returning PaginateArrayResult<T> (data, total, totalPages, hasNext, hasPrev)
  • Validated pageSize to be between 1 and 200, throwing SdkError with SdkErrorCode.INVALID_RECIPIENT when invalid
  • Handled out-of-range page requests returning data: [] without errors
  • Exported PaginateArrayOptions and PaginateArrayResult types
• [MODIFY] src/index.ts
  • Exported paginateArray, PaginateArrayOptions, and PaginateArrayResult on the public SDK entrypoint
• [MODIFY] test/horizonPaginator.test.ts
  • Added unit tests covering:
    • First page, middle page, last page
    • Out-of-range page beyond totalPages and page < 1 returning empty array
    • Single item array and array with exactly pageSize items
    • Empty array edge case
    • hasNext and hasPrev correctness across pages
    • Throwing SdkError with INVALID_RECIPIENT code when pageSize < 1 or pageSize > 200 or non-integer
    • Boundary values for pageSize = 1 and pageSize = 200
    • Generic array typing with custom interfaces (Invoice[], Payment[])

Acceptance Criteria Checklist

• paginateArray<T>(items: T[], opts: { page: number; pageSize: number }): { data: T[]; total: number; totalPages: number; hasNext: boolean; hasPrev: boolean } exported from src/horizonPaginator.ts
• page is 1-indexed; page=1 returns the first pageSize items
• Out-of-range page (beyond totalPages) returns data: [] without error
• pageSize must be between 1 and 200 — throws SdkError with INVALID_RECIPIENT code otherwise
• Exported from src/index.ts
• Unit tests: first page, last page, out-of-range page returns empty, single item, exactly pageSize items, hasNext/hasPrev correctness

Verification Results

 RUN  v1.6.1 /Users/solveetcoagula/Desktop/activeProjects/bounty_operations/split-sdk-618

 ✓ test/horizonPaginator.test.ts  (37 tests) 7ms

 Test Files  1 passed (1)
      Tests  37 passed (37)

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