fix: use unscoped npm package name

[BenKalsky]

Summary

• Renames npm package from @godigitizer/sumit-react to unscoped sumit-react
• Updates peer/dev dependency and imports to unscoped sumit-api
• Updates README/agent docs install and import examples
• Keeps GitHub repo under Digitizers; npm package publishes under the godigitizer user account

Test Plan

• corepack pnpm install --lockfile-only
• corepack pnpm install --frozen-lockfile
• corepack pnpm test
• corepack pnpm typecheck
• corepack pnpm build
• npm pack --dry-run