docs: confirm Vulkan device enumeration and close the Bazzite setup check

vulkaninfo names GPU0 as the discrete RTX 5070 Ti (NVIDIA 615.78.08, API
1.4.351), with the RADV iGPU as GPU1 and llvmpipe as GPU2. Note the device
selection risk for the engine and mark the ROADMAP environment item done.

Docs/toolchain.md

@@ -9,7 +9,7 @@ Audited 2026-11-06 on the development workstation.
 | Component | Pinned | Source | Status |
 | --- | --- | --- | --- |
 | Bazzite | `45.20261105` (Kinoite, `bazzite-dx-nvidia`), kernel `7.2.15-ogc1.1.fc45` | `ujust update` / `rpm-ostree upgrade` | Booted and default. `44.20261026` retained as rollback. |
-| NVIDIA driver | `615.78.08`, open kernel module | Bazzite image | Verified: desktop session renders through the RTX 5070 Ti; Vulkan instance 1.4.350. Vulkan device-name capture still pending, see [environment.md](environment.md). |
+| NVIDIA driver | `615.78.08`, open kernel module | Bazzite image | Verified: desktop session renders through the RTX 5070 Ti; Vulkan GPU0 is the RTX 5070 Ti on driver `615.78.08`, conformance `1.4.3.3`. |
 | Unreal Engine | `5.8.x` — pin one exact build | Epic (license required) | Not installed. |
 | Unreal Linux toolchain | engine-bundled clang | Engine source tree | Not installed. Do not substitute the system compiler. |
 | Blender | `5.2` LTS (upstream patch `5.2.3`) | Flatpak `org.blender.Blender` | Installed. |