chore: pnpm upgrade

[craigzour]

Summary | Résumé

• Upgrades PNPM to version 11.8.0
• Simplifies CI test workflow with a single check command that runs both formatter and linter sub commands
• Upgrades Github checkout action to version 7.0.0 (starting to upgrade some sub dependencies due to deprecation of Node20 in Github Actions https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners)
• Resolves lint issues by letting Biome reorganize imports when we save a file