Unify the test runners used across the repository

[priscaenoch]

Problem

The repository uses two different test runners:

• The root TypeScript API service uses Vitest (vitest.config.ts, npm test).
• The indexer/ service uses Jest (indexer/jest.config.js).

Two runners means two configuration formats, two sets of conventions, duplicated mocking/setup knowledge, and two coverage mechanisms for contributors to learn. It also complicates the CI work needed to cover both services.

What needs to be done

• Decide on one runner for the repository (Vitest is the likely target since the root already uses it and it supports plain JS).
• Migrate the other service's tests, keeping behaviour identical: config, setup files, mocks, and coverage.
• Verify all roughly 47 indexer tests still pass after migration.
• Update CI and the contributing docs to reference a single command.
• If the two runners must remain, document the rationale and the boundary explicitly instead.

Files

• vitest.config.ts
• indexer/jest.config.js
• indexer/package.json, package.json
• .github/workflows/ci.yml, CONTRIBUTING.md

Acceptance deliverables

• A single documented test runner and command, or a documented, deliberate exception.
• No test regressions after the migration.

Tests to pass

• The full suite for both services passes under the unified runner.

[adamfishman03-star]

i will like to work on this issue based on my experience

[grantfox-oss]

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Next steps:

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