fix: publish Madrigal under Anarchitecture npm scope

[nahiyankhan]

Summary

• Changes the npm package from @block/madrigal to @anarchitecture/madrigal.
• Updates README examples, Changesets docs, and changelog heading to the corrected scope.
• Keeps the CLI binary name as madrigal.

Root Cause

The follow-up release failed because @block/madrigal is not the npm scope configured for this package. The package should publish under the @anarchitecture scope instead.

Verification

• curl -L -s https://registry.npmjs.org/@anarchitecture%2fmadrigal returned {"error":"Not found"} before publish, which is expected for the first publish.
• pnpm build
• pnpm check
• pnpm typecheck
• pnpm test
• npm pack --dry-run --ignore-scripts --access public --cache=/private/tmp/madrigal-npm-cache --loglevel=notice reports @anarchitecture/madrigal@0.1.0
• pre-commit hook: biome check .
• pre-push hook: pnpm vitest run, pnpm biome check ., pnpm tsc --noEmit

Note

The next Release workflow still requires MADRIGAL_NPM_PUBLISH_TOKEN to have publish permission for the @anarchitecture npm scope.