Task: Replace `mocha` with `vitest` for SVelte tests

# Task: Replace `mocha` with `vitest` for Svelte Tests

## Description  

`mocha` as the testsuite is no longer compatible for executing tests when the updated Svelte 5 _runes_ exist within a testable source.

Using `vitest` would be a complete, and compatible, solution as it is used alongside `vite`. I feel that this would be the best solution given that `vite` is now being used as a packaging dependency.

## Acceptance Criteria  

`vitest` is successfully replaced for `mocha`/`chai` and all of the SVelte tests that exist and can execute while accurately reporting test case results.

## Additional Information

~~I have tested this locally and all of the test files execute with `vitest`, even the non Svelte files.~~
**Update**
I originally had all tests executing and reporting correct results but upon inspecting under the hood of the native VSCode Test Explorer I found that it was smart enough to pull in mocha to run those tests within the `./src/tests/` directory.

`vitest` does not have to capability to provide the VSCode API due runtime dependency issues. `mocha` will still have to be used for those tests