`_total_ram_gb()` had branches for Darwin (sysctl) and Linux
(/proc/meminfo) but no Windows path, so `jarvis init` reported
"0.0 GB RAM" on every Windows host. The downstream
`recommend_model()` then fell back to VRAM-only sizing, often
selecting a smaller tier than the system can actually run.
Add a Windows branch that calls `GlobalMemoryStatusEx` via
ctypes — no new dependency. Add a platform-skip-aware test for
each OS branch.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>