bootstrap: finish project bootstrap — scale test, MPFB character, build docs

- Static-mesh scale test passes: 1 m = 100.00 cm, origin preserved, axis
  mapping east→+X / north→−Y / up→+Z (named presets ue_metric_v1 both sides).
- MPFB 2.0.18 acceptance passes: generated human + standard 137-bone rig
  with weights + v2 skin baked to 1024² diffuse; imports as SkeletalMesh
  with Skeleton, Material, and Texture2D in /Game/Test/Character.
- MPFB headless requires XDG_CONFIG_HOME at the Flatpak config tree;
  documented in Art/blender/README.md, probe in Tools/addon_compat_probe.py.
- Docs/build.md completed: fresh-checkout build, packaging, headless checks.
- Docs/setup.md reconciled with reality; ROADMAP/bootstrap closed out.

Docs/toolchain.md

@@ -13,7 +13,7 @@ Audited 2026-11-06, updated 2026-11-07 on the development workstation.
 | 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). **Validated 2026-11-07:** headless `-NullRHI` smoke test and full editor GUI launch with Vulkan RHI on the RTX 5070 Ti (loader 1.4.350, `VULKAN_SM5`, map check 0 errors). Pin is final. The verified 5.2.0 archive stays as fallback. |
 | 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. **Accepted 2026-11-07:** first game-module compile and link succeeded (`GigLineEditor` target, `libUnrealEditor-GigLine.so`). Note: game targets must use `BuildSettingsVersion.V7` to share the engine's build environment. |
 | 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. |
+| MPFB | `2.0.18` (extension `bl_ext.blender_org.mpfb`, `blender_version_min 4.2.0`) | Blender extensions platform | Installed. **Headless-verified 2026-11-07 on 5.2:** enables and generates a default human (19 158-vert mesh, UVs) via `Tools/addon_compat_probe.py`. Headless runs must set `XDG_CONFIG_HOME=$HOME/.var/app/org.blender.Blender/config` or the extension is not discovered (see `Art/blender/README.md`). Load-and-export (skeleton + baked materials) check 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. Stale `lts` branch (`3.28.9`, EOL Qt5 runtime) uninstalled 2026-11-07; only `stable` remains. |
 | Git | `2.56.0` | Bazzite image | Installed. |
@@ -48,6 +48,6 @@ To update: copy `.claude/skills/` from a newer upstream checkout over the existi
 ## Open compatibility risks
 
 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.
+2. **MPFB 2.0.18 on Blender 5.2.** The extension declares Blender >= 4.2 but predates 5.x. Generation verified 2026-11-07: `mpfb.create_human` works headless once `XDG_CONFIG_HOME` points at the Flatpak config tree. Remaining 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. **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.