replace npm/nvm with pnpm/mise

[viqueen]

Summary

• Replace npm with pnpm as the package manager
• Replace nvm with mise for tooling (node, pnpm) version management
• Pin node 24.12.0 and pnpm 10.30.3 in .mise.toml

Test plan

• Run mise trust && mise install to set up tooling
• Run pnpm install to verify dependencies resolve
• Run pnpm run format:check to verify pre-commit hook works

🤖 Generated with Claude Code

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud