Add VM guest services and display adapter detection

[jgowdy-godaddy]

Summary

Follow-up to #164. Adds two new detection categories lifted from vmaware's methodology (artifact-based checks only, no CPUID scoring):

• Guest services: Check for 30+ VM-specific Windows services in the registry (vmicheartbeat, VBoxGuest, vmci, vioscsi, etc.). These services are only installed by hypervisor guest tools — never present on bare metal.
• Display adapter: Check the primary GPU driver description for known virtual adapters (Hyper-V Video, VMware SVGA, VirtualBox Graphics, QXL, etc.)

Both are exposed in VmDiagnostics for consumer diagnostic logging.

Design notes

• Deliberately did NOT use vmaware as a dependency — its default classifier false-positives on VBS/Hyper-V physical machines (hypervisor bit = 100 points, threshold = 150)
• Only lifted the guest-artifact checks which have zero false-positive risk on physical hardware
• Guest services check runs early in detection (after BIOS strings, before CPUID) because it's highly conclusive

Test plan

• 51 tests pass including new vm_display_signal tests
• Clippy clean, fmt clean
• Verify on Hyper-V VM: vmicheartbeat service detected
• Verify on physical VBS machine: no guest services found