feat: ship sandcode cli

[anand-testcompare]

Summary

• rename and package the project as sandcode with a single Bun-powered CLI entrypoint
• add the OpenTUI-based setup flow, Sandcode config rename, and npm/trusted-publishing release workflow
• refresh docs, install/build scripts, and CI/package E2E coverage around the new package surface

Testing

• bun run check
• bun run typecheck
• bun test
• bun run build
• npm pack --pack-destination .memory/release-check
• installed tarball smoke in /home/anandpant/Development/agentic-development/sandcode-testing/local-package-e2e-20260307-4