v3.1.0

Fix setup-atmos Windows installs Erik Osterman (Cloud Posse) (@osterman) (#111)

## what * Fix release asset parsing for Windows `.exe` assets and install runnable `atmos.exe`/wrapper shims across OSes. * Add checksum validation input defaulting to `warn`, 80% coverage enforcement, expanded Jest tests, and OS/mode CI matrix. * Rebuild committed `dist/` artifacts.

why

• Windows runners need atmos immediately after setup for wrapper and no-wrapper modes.
• Checksum validation catches corrupted downloads while preserving current behavior when checksums are missing.

references

• Validation: npm run format:check, npm run lint:check, npm run test:coverage -- --runInBand, npm run clean && npm run build && npm run build:wrapper.