Add native and Docker runtime distributions

[flemming-n-larsen]

Summary

• add native ZIP/TAR distributions and a no-install runtime prerequisite check for Java 17, .NET 8, Python 3.12, and Node.js 22
• add a non-published Docker development image and constrained PowerShell/POSIX launchers
• accept the optional immutable engine.json.clientImage guidance introduced by Tank Royale CH-012
• test native builds on Windows, macOS, and Linux and smoke-test the non-root, read-only image without network access

Scope

This is the distribution foundation for Tank Royale CH-012 / P-003 M-008. Battle execution and issue-ops submission remain unavailable and the README states that explicitly. No production image is published until Tank Royale releases the M-005 engine contracts.

Verification

• ./gradlew clean build
• PowerShell parser check for docker/rumble.ps1
• bash -n docker/rumble.sh
• git diff --check

Docker build and smoke verification run in this PR's GitHub Actions because Docker is not installed on the development machine.