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.