feat(Build): modernize build and test tooling with Vite/Vitest & oxlint/oxfmt

[daker]

Context

This PR completes a tooling migration from the legacy webpack/rollup + Karma/Tape setup to a unified Vite + Vitest stack. It updates local development, build output, test execution, and CI integration to run on the new toolchain.

Results

• Reduce maintenance overhead from multiple legacy build/test systems.
• Standardize on a modern, faster toolchain for both local and CI workflows.
• Improve consistency between build and test environments by sharing Vite-based config.
• Remove UMD build.
• Everything should works as before.

Changes

• Replaced legacy build configuration with vite.config.js.
• Added Vitest browser-runner configuration via vitest.config.js.
• Migrated test infrastructure and tests to Vitest.
• Removed old webpack, rollup-legacy, and Karma-related configs/plugins/utilities.
• Migrate ExampleRunner to vite devserver.
• Updated GitHub Actions workflows to run the Vite/Vitest pipeline.
• Updated dependencies and lockfile to reflect the new build/test stack.
• Documentation and TypeScript definitions were updated to match those changes

PR and Code Checklist

• semantic-release commit messages
• Run npm run reformat to have correctly formatted code

Testing

• This change adds or fixes unit tests
• Tested environment:
  • vtk.js:
  • OS:
  • Browser:

[daker]

@finetjul @jourdain it's ready for review