test: implement unit tests

[nipsysdev]

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[Copilot]

Pull Request Overview

This PR sets up Vitest and adds a comprehensive suite of unit tests across utilities, hooks, contexts, and components, alongside the necessary configuration and CI updates.

• Introduce vitest.config.mjs and test setup.
• Add tests for all utility functions, hooks, contexts, and UI components.
• Update package.json, Lefthook config, and GitHub workflow to integrate testing.

Reviewed Changes

Copilot reviewed 43 out of 44 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
vitest.config.mjs	Configure Vitest for unit testing and coverage
package.json	Add test scripts, devDependencies for Vitest & RTL
lefthook.yml	Define pre-commit and pre-push hooks invoking tests
lefthook.yaml	Now empty/duplicate config
.github/workflows/check.yml	Add test job to run tests in CI

Files not reviewed (1)

• pnpm-lock.yaml: Language not supported

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