feat(device): collect static machine resource info

[swarit-stepsecurity]

Summary

Adds CPU model / physical+logical cores / architecture, total RAM, and root volume capacity to the device snapshot reported on every scan. High-signal answer to "how much resource does this machine have" — no volatile fields (free RAM, per-process load) that would muddy a static snapshot.

DEVICE
  Hostname    EC2AMAZ-HJS7CVB
  Serial      ec241363-fe37-f981-a408-72c4cfdf51c7
  Windows     10.0.26100
  User        EC2AMAZ-HJS7CVB\Administrator
  CPU         Intel(R) Xeon(R) Platinum 8175M CPU @ 2.50GHz (1c / 2t, amd64)
  Memory      7 GB
  Disk        99 GB

Implementation

• New model.MachineResources struct embedded as Device.Resources — single nested key, additive change.
• internal/device/resources.{go,_other.go,_windows.go} follow the existing platform-split convention in this package.
  • Linux: /proc/cpuinfo + /proc/meminfo (no subprocess). Graceful ARM degradation — falls back to Hardware/Model lines and reports physical_cores: 0 rather than misreporting.
  • macOS: sysctl machdep.cpu.brand_string, hw.physicalcpu, hw.logicalcpu, hw.memsize.
  • Windows: native Win32 APIs (registry ProcessorNameString, GetLogicalProcessorInformation, GlobalMemoryStatusEx, GetDiskFreeSpaceEx) with PowerShell Get-CimInstance as the only fallback. wmic is no longer available on Win11 / Server 2025 and was deliberately not used.
• Disk capacity goes through a new Executor.DiskCapacityBytes(path) uint64 method (syscall.Statfs on unix, GetDiskFreeSpaceEx on windows) so it stays mockable like every other OS interaction.
• Surfaced in pretty + HTML output and added to the enterprise telemetry Payload.
• Tests cover parsers (x86, ARM, multi-socket, malformed), all three OS code paths via SetGOOS, and missing-file degradation.

Test plan

• go test ./... — full suite green
• go vet ./... clean
• Cross-compile verified for darwin/amd64+arm64, linux/amd64+arm64, windows/amd64
• macOS host (M4 Pro MBP): numbers match local hardware
• Linux (Fedora 42 EC2 t3.xlarge): matches nproc (4), free -h (15Gi), df -h / (29G)
• Windows (Server 2025 EC2 t3.large): matches Get-CimInstance Win32_Processor (1c/2t Xeon 8175M) and Win32_ComputerSystem (8.36 GB / 99.5 GB)