chore: refresh dependency tooling

[nawforce]

Summary

Refreshes git-ops dependency and workflow tooling for the next normal release.

• bump package version to 1.4.2
• refresh TypeScript / ESLint tooling and migrate to flat config
• refresh GitHub Actions workflow versions
• update pnpm lockfile and package-manager metadata
• split build and ESLint TS configs so TS 6 works cleanly with package build and type-aware test linting
• update test matcher aliases for Jest 30 compatibility
• keep runtime @salesforce/core on ^4.3.11

Validation

• pnpm install --no-frozen-lockfile
• npm run build
• npm run lint
• npm test

Release note

This is a normal patch release candidate for 1.4.2, not a beta.