refactor(tools): group the sixty scripts by what they talk to

One directory with sixty scripts stopped being navigable, and the grouping is also the sandbox boundary:

  Tools/unreal/    commandlets and the two map builders, with ue_common.py and ue_placement.py as the
                   shared imports (they need the engine)
  Tools/blender/   builders, exporters, the FBX preset, the MPFB character pipeline, blender_screenshots
                   (they need the Blender Flatpak)
  Tools/review/    the visual loop: render_screenshots.sh, judge_screenshot.py, hero_compare.py,
                   build_comparison_md.py, e2e_asset_check.py, hero_iterate.sh, visual_loop.py,
                   visual_targets.json
  Tools/gen/       image and texture generation: the ComfyUI driver, deterministic texture writers,
                   reference fetching
  Tools/input/     OS-level input injection
  root             _common.py, check-lfs.sh, addon_compat_probe.py, sibling_asset_audit.py, tests/

Every moved script now resolves the repository root as ../.. and puts the tools root plus its siblings on
sys.path, so 'import ue_common' still works from unreal/. The test suite bootstrap does the same for the five
folders. render_screenshots.sh takes the folder as a third argument to run_cmdlet, and the e2e driver,
hero_iterate.sh and the comparison generator were repointed.

51 README rows now link to their new location, the README gains a Layout section naming each folder's
sandbox, and the architecture notes and Blender README follow the moves.

Verified: 108 tests pass, prettier is clean, judge_screenshot.py and hero_compare.py run from their new
homes, and the e2e run was aborted mid-way (it had been rebuilding an empty DemoMap for 15 minutes) and is
being rerun against the new layout.

THIRD_PARTY_NOTICES.md

@@ -31,7 +31,7 @@ Reference photographs are **not** part of this repository. They live in the giti
 | Local folder | Source | Provenance |
 | --- | --- | --- |
 | `Art/reference/hollywood/` | Copied 2026-11-06 from `…/06-games/security-game/docs/screens/refs/hollywood/` | That folder's `SIDECAR.md` (author, licence, URL, crop notes) |
-| `Art/reference/north-chinese/` | Fetched 2026-11-06 with `Tools/commons_fetch.py` from the Wikimedia Commons API | `sidecar.json` in the folder |
+| `Art/reference/north-chinese/` | Fetched 2026-11-06 with `Tools/gen/commons_fetch.py` from the Wikimedia Commons API | `sidecar.json` in the folder |
 | `Art/reference/north-tussauds/` | Same | `sidecar.json` in the folder |
 
 Reference notes and images are local only and excluded from version control.
@@ -46,9 +46,9 @@ Rules that still apply, because they are about shipped output rather than local
 
 | Component | Source | Licence | Status |
 | --- | --- | --- | --- |
-| Character mesh, standard rig, and baked skin | MPFB 2.0.18 bundled base mesh, rig, and textures; `Tools/mpfb_character_export.py` | CC0 1.0 for bundled assets | [x] against the [versioned MPFB licence](https://github.com/makehumancommunity/mpfb2/blob/v2.0.18/LICENSE.md); imported character assets and Blender source are tracked. |
+| Character mesh, standard rig, and baked skin | MPFB 2.0.18 bundled base mesh, rig, and textures; `Tools/blender/mpfb_character_export.py` | CC0 1.0 for bundled assets | [x] against the [versioned MPFB licence](https://github.com/makehumancommunity/mpfb2/blob/v2.0.18/LICENSE.md); imported character assets and Blender source are tracked. |
 | OSM blockout | OSM extract and Blosm-generated geometry | OpenStreetMap data, local private use | Source manifests in `Geo/manifests/`. |
 | Terrain and street prototype | USGS 3DEP DEM, OSM data, project scripts | Public domain USGS data; OpenStreetMap data, local private use | Source manifests in `Geo/manifests/`. |
-| Hero façade blockout | Project-owned geometry from `Tools/hero_facade_build.py`, dimensions from OSM and the reference photography | Project-owned | Committed with a per-part evidence report (`Art/blender/hero/hero-facade-*.json`) and a position sidecar (`hero-facade.geo.json`). |
+| Hero façade blockout | Project-owned geometry from `Tools/blender/hero_facade_build.py`, dimensions from OSM and the reference photography | Project-owned | Committed with a per-part evidence report (`Art/blender/hero/hero-facade-*.json`) and a position sidecar (`hero-facade.geo.json`). |
 | Street props (candidate reuse) | Sibling project `…/06-games/security-game`, `assets/models/blender_src/*.blend` | Project-owned by the same author | **Not yet imported.** Sources copied to `Art/props/blender_src/` with `Art/props/reuse-manifest.json`; a licence statement is required before any of them ship. |
 | Hero façade stone albedo | `Art/textures/generated/T_FacadeAshlar_AI.png`, generated locally with ComfyUI (Stability Matrix, `/home/zwitschi/StabilityMatrix/Data/README.md`) using **AlbedoBase XL v3.1-Large** at seed 21, workflow `texture_albedobase_xl` | Civitai model 140737 — commercial image use allowed, credit required | [ ] credit line still to be added to the game's credits document before release; sidecar `T_FacadeAshlar_AI.json` records model, prompt, seed and graph |