Arcadia Studio portable Windows bundle

Open arcadia-studio.exe. See docs/windows-packaging.md for runtime prerequisites
and verification, README.md for model workflows, and docs/server.md to run the
optional arcadia-server.exe. Examples are under examples/; Help is built in.

Keep the bundled runtime DLL beside both executables when present. No compiler
installation or machine PATH change is required by the staged runtime closure.
This binary bundle does not include repository sources needed for Cargo/Docker
build commands. Packaging integrity is not native release acceptance; read
package.json and the distributor's binary-specific acceptance record for limitations.
