docs: add the memory convention and seed MEMORY.md

AGENTS.md now states that planned work is checkbox items in ROADMAP.md marked
open, in progress, or done, and that discoveries, gotchas, notes, and bugs go to
MEMORY.md for coordination between collaborators. MEMORY.md is seeded with what
this build-up actually cost: the Unreal read-only-home crash, Blender/Blosm
headless workarounds and the spherical projection, the tiled-TIFF DEM trap, the
reference licensing and throttling rules, and the LFS silent-blob trap.

Also stages the concurrently created Unreal project files, and stops per-project
Build/ output (FileOpenOrder logs) from entering the repository.

Docs/toolchain.md

@@ -10,8 +10,8 @@ Audited 2026-11-06, updated 2026-11-07 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` — 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. |
+| 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. |
 | 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. |