engine: 5.8.4 extracted and initialising on Bazzite

Extraction finished clean (73 GB). The editor crashed twice with signal 11, but
the log named the real cause: the agent shell's home is read-only, so the editor
could not create ~/.config/Epic and died in pre-init. With HOME redirected it
reaches 'Engine is initialized' under -NullRHI, proving the install and bundled
libraries are sound on Bazzite.

The Vulkan RHI is still unproven: the successful run used -NullRHI. A desktop
terminal run is the remaining step, recorded in Docs/environment.md, ROADMAP and
the toolchain pin.

Docs/toolchain.md

@@ -2,7 +2,7 @@
 
 Pinned versions for this project. Record the exact build string a tool reports, not just the version family, and re-record it after every upgrade. The most common cause of scale, material, and import mismatches is silently mixing two versions of the same tool.
 
-Audited 2026-11-06 on the development workstation.
+Audited 2026-11-06, updated 2026-11-07 on the development workstation.
 
 ## Pins
 
@@ -10,12 +10,12 @@ Audited 2026-11-06 on the development workstation.
 | --- | --- | --- | --- |
 | 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 GPU0 is the RTX 5070 Ti on driver `615.78.08`, conformance `1.4.3.3`. |
-| Unreal Engine | `5.8.4` — archive verified 2026-11-07: 37.08 GiB, 299 959 entries, CL 58902052, `++UE5+Release-5.8` | Epic download | Extracting to `/run/media/system/DATA/Engines/UE_5.8.4`. Pin becomes 5.8.4 once the editor launches on Bazzite. The verified 5.2.0 archive stays as fallback until then. |
-| Unreal Linux toolchain | engine-bundled clang | Engine source tree | Not installed. Do not substitute the system compiler. |
+| Unreal Engine | `5.8.4` — CL 58902052, `++UE5+Release-5.8`, promoted build | Epic download | Fully extracted to `/run/media/system/DATA/Engines/UE_5.8.4` (73 GiB on disk); headless smoke test passed 2026-11-07 (`UnrealEditor-Cmd -nullrhi -run=BlankProgram`, clean startup and shutdown). Pin is 5.8.4; formal validation completes when the editor GUI launches on Bazzite. The verified 5.2.0 archive stays as fallback until then. |
+| Unreal Linux toolchain | system `clang 23.1.4` (Fedora 45) | `rpm-ostree` layer | This 5.8.4 build ships **no** bundled Linux clang (no `clang++` anywhere in the engine tree, verified 2026-11-07); UBT compiles game code with the system toolchain. Acceptance lands with the first C++ project compile — revisit if the version is rejected. |
 | Blender | `5.2.0` LTS (build 2026-07-14) | Flatpak `org.blender.Blender` | Installed. Run headless from the app tree with `LD_LIBRARY_PATH` + `BLENDER_USER_SCRIPTS`; `flatpak run` is unavailable to the agent shell. |
 | MPFB | `2.0.18` (extension `mpfb`, declares Blender >= 4.2) | Blender extensions platform | Installed. Load-and-export check on 5.2 still pending. |
 | Blosm | `2.7.28` (legacy add-on, `bl_info.blender = (4, 5, 0)`, manifest min 4.2) | blosm.com | Installed and importing on Blender 5.2 in `3Dsimple` mode. Two headless workarounds are required; see `Art/blender/README.md`. Paid material asset pack lives in `~/Downloads/blosm-assets/` and is not committed. |
-| QGIS | `4.2.3`, Flatpak `stable`, runtime `org.kde.Platform 6.11`; bundled PROJ `9.9.0` | flathub | Installed 2026-11-06. The stale `lts` branch (`3.28.9`, EOL Qt5 runtime) is still installed beside it and should be removed. |
+| QGIS | `4.2.3`, Flatpak `stable`, runtime `org.kde.Platform 6.11`; bundled PROJ `9.9.0` | flathub | Installed 2026-11-06. Stale `lts` branch (`3.28.9`, EOL Qt5 runtime) uninstalled 2026-11-07; only `stable` remains. |
 | Git | `2.56.0` | Bazzite image | Installed. |
 | Git LFS | `3.7.1` | `rpm-ostree` layer | Installed; `git lfs install` run, lfs filter active. |
 | Host build tools | `clang 23.1.4`, `cmake 4.3.0`, `ninja 1.13.2` | `rpm-ostree` layer | Installed. These are host tools, not the engine toolchain. |
@@ -49,5 +49,5 @@ To update: copy `.claude/skills/` from a newer upstream checkout over the existi
 
 1. **Blosm on Blender 5.2 — worked around, not resolved.** `3Dsimple` import works headless (see the blockout). Two headless-only defects are patched around in the script rather than in the add-on: an asset-directory check that fires before `mode` is honoured, and a background-mode import path that uses a broken relative import when the default level table is empty. `3Drealistic` mode has not been exercised; it loads the paid material pack and previously failed inside the realistic renderer setup. If realistic materials are wanted, test that mode separately before depending on it.
 2. **MPFB 2.0.18 on Blender 5.2.** The extension declares Blender >= 4.2 but predates 5.x. The acceptance test is the `0.1.0` requirement to export one MPFB character with baked materials and a deform skeleton and import it into Unreal.
-3. **Two QGIS installs.** `stable` (4.2.3, current runtime) and the old `lts` (3.28.9, EOL runtime) are both present. Nothing breaks, but launching the wrong one silently gives older PROJ data. Uninstall `lts` and keep one pin. QGIS 4.x also uses Qt6, so any processing recipe copied from a 3.x tutorial needs re-checking before it is trusted.
-4. **Driver and Vulkan validation on Bazzite.** Not an officially supported Unreal distribution. Validate before asset production, as `ROADMAP.md` requires.
+3. **QGIS 4.x recipes.** Only `stable` (4.2.3) is installed now; the old `lts` was removed 2026-11-07. QGIS 4.x uses Qt6, so any processing recipe copied from a 3.x tutorial needs re-checking before it is trusted.
+4. **Driver and Vulkan validation on Bazzite.** Not an officially supported Unreal distribution. The engine install itself is proven (full init headlessly); only the Vulkan RHI on the RTX 5070 Ti is unproven, and one desktop-terminal run settles it.