kinduino v0.5.2

Private-beta build. Assets: the Boards-Manager index (package_kindle_index.json) + host CLIs (macOS arm64/x86_64, Linux, Windows), the pinned Zig toolchain, the platform archive, and the on-device runtime zip (kinduino-device-*.zip, installed via KUAL). See docs/getting-started.md and docs/building-from-source.md.