P3: Cluster build-toolchain provisioning for new-language competitors (ansible, manifest-tracked)

[FumingPower3925]

Part of #151.

Why. New competitors need build toolchains on the cluster nodes (or cross-built + staged). Per the cluster-pristine rule, every install must be ansible-driven with manifest cleanup — NEVER hand-installed.

Scope.

• Extend deploy/provisioning playbooks to install (idempotently, manifest-tracked, with matching uninstall in mage Cleanup): Zig (for the architectural-peer issue), and for the TechEmpower-leaders issue: .NET SDK, a JVM (+ Vert.x/Netty build), Node (uWebSockets.js), C++ toolchain + cmake (drogon). Rust/Bun/Python already provisioned.
• Prefer cross-compile + stage prebuilt binaries from the dev Mac / CI where feasible (as Rust does via release-fat), to keep nodes pristine + provisioning fast.
• Cross-arch: native binaries built for BOTH amd64 (msa2-server) and arm64 (msr1).
• Update mage status / manifest to show staged competitor binaries per arch.

Acceptance. mage Deploy stages every competitor binary for both arches; mage Cleanup removes all of it + the toolchains; mage status reflects state.

Refs: ansible/deploy.yml, mage_cluster.go, cluster-pristine rule.