Align the Intel display identity and validate the VRAM override

docs/PLATFORM_IDENTITY.md

@@ -160,6 +160,8 @@ commands.
 `SPDisplaysDataType` reads the host DRM cards. With `DARLING_METAL_MAC_GPU_NAME`
 set (the launcher default), an AMD or NVIDIA host card is reported as the
 `MacBookPro16,1` discrete GPU: `AMD Radeon Pro 5500M`, vendor `0x1002`, device
-`0x7340`, bus PCIe and VRAM from `DARLING_METAL_VRAM_MB` (4096 by default). This
-keeps the display report consistent with `MTLDevice.name`; without the variable
-the host card is reported as-is.
+`0x7340`, bus PCIe and VRAM from `DARLING_METAL_VRAM_MB` (4096 by default; a
+value that is not a positive decimal keeps the default). An Intel card is
+reported as `Intel UHD Graphics 630` on bus Built-In with shared memory, as
+`MTLDevice.name` does. This keeps the display report consistent with Metal;
+without the variable the host card is reported as-is.

tools/darling-system_profiler.sh

@@ -52,7 +52,12 @@ displays() { # one line per GPU: vendor|device|vram MB or empty|name|bus
   if [ "$mac_spoof" = 1 ]; then
    case "$vendor" in
     1002|10de) vendor=1002; device=7340; name='AMD Radeon Pro 5500M'
-               vram=${DARLING_METAL_VRAM_MB:-4096}; bus=pcie;;
+               vram=${DARLING_METAL_VRAM_MB:-4096}
+               case "$vram" in ''|*[!0-9]*) vram=4096;; esac
+               [ "$vram" -eq 0 ] 2>/dev/null && vram=4096
+               bus=pcie;;
+    8086) vendor=8086; device=3e9b; name='Intel UHD Graphics 630'
+          vram=; bus=builtin;;
    esac
   fi
   echo "$vendor|$device|$vram|$name|$bus"