docs: clarify Graphic card setting for GPU passthrough VMs

VMs with a passed-through GPU need Graphic card set to 'none' —
VirtIO-GPU conflicts with the real card. VMs without GPU keep
default VirtIO for console access. Add this to VM 100 and VM 101
System tab tables with explanatory notes.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

README.md

@@ -2132,6 +2132,7 @@ Click **Next**.
 
 | Field | Value |
 |-------|-------|
+| Graphic card | **Default** (VirtIO) |
 | Machine | q35 |
 | BIOS | OVMF (UEFI) |
 | Add EFI Disk | checked |
@@ -2146,6 +2147,9 @@ Click **Next**.
 > **Pre-Enrolled Keys must be unchecked.** Enabling it turns on Secure Boot,
 > which blocks NVIDIA kernel modules from loading in the guest.
 
+> **Graphic card stays as Default (VirtIO) for VM 100** — Frigate has no
+> passed-through GPU, so it needs the virtual display for console access.
+
 Click **Next**.
 
 **Tab: Disks**
@@ -2359,10 +2363,18 @@ Click **Create VM** in the web UI.
 |-----|-------|
 | General | VM ID: **101**, Name: **vm101** |
 | OS | ubuntu-24.04.4-desktop-amd64.iso |
+| System → Graphic card | **none** |
+| System → Machine | q35 |
+| System → BIOS | OVMF (UEFI) |
+| System → Pre-Enrolled Keys | **unchecked** |
 | CPU | 8 cores, host |
 | Memory | 16384 MiB |
 | Disk | 64 GiB on local-lvm |
 
+> **Graphic card must be set to "none"** when passing through a real GPU.
+> Leaving it as VirtIO-GPU creates a conflicting virtual display adapter that
+> interferes with the passed-through card.
+
 After the wizard completes, add the GPU in the **Hardware** tab:
 
 Click **Add** → **PCI Device**.