test(scripts): add unit tests for retry/rate-limit utils + fix Jest config under ESM

[ash-balla]

Summary

Adds unit tests for two previously-untested utility modules in scripts/, and fixes the Jest configuration so the test runner actually works.

While adding tests I found that the existing Jest setup could not run at all: jest.config.js used CommonJS module.exports, but scripts/package.json declares "type": "module", so Node parsed the config as ESM and threw:

ReferenceError: module is not defined in ES module scope

This prevented every Jest test (including the existing test/data_models.test.ts) from executing — consistent with the "Unit Tests (To be implemented)" note in scripts/README.md. Renaming the config to jest.config.cjs resolves it (Jest auto-discovers .cjs).

Changes

• Rename scripts/jest.config.js → scripts/jest.config.cjs (same contents) so the config loads as CommonJS under "type": "module".
• Add scripts/test/retry_utils.test.ts — 13 tests for retryWithBackoff:
  • returns immediately on first-attempt success
  • retries on a retryable error then resolves
  • throws immediately on non-retryable errors (no retry)
  • exhausts retries (default 3 → 4 attempts; custom maxRetries; returns the last error)
  • detects retryable errors via error.code, error.status, error.name, and message text
  • honors a custom retryableErrors list (and overrides defaults)
  • verifies exponential backoff with maxDelay capping (delays [100, 200, 400, 500])
• Add scripts/test/rate_limit_utils.test.ts — 8 tests:
  • processBatch: preserves order across batches, handles empty input, handles an oversized batch size, and runs items within a batch in parallel
  • checkRateLimit: queries the API once per 10 calls, pauses when remaining is below threshold, does not pause when above, and tolerates a failing rate-limit lookup without throwing

Test Results

All suites pass:

Test Suites: 3 passed, 3 total
Tests:       34 passed, 34 total

Jest exit code 0.

Notes

• Tests follow the existing test/data_models.test.ts conventions (TypeScript, describe/it, imports without .js extension).
• No production/runtime code was changed — this PR only adds tests and fixes the test-runner config.