#729: import STL 3D models (binary and ASCII)

Problem: After Effects 26 imports STL models besides glTF and OBJ; we
refused .stl files, and the Media Browser and import dialog did not list
them as models.

Fix: a pure-Rust STL reader in effectcraft-model (binary and ASCII,
detected from the contents; several ASCII solids and polygon loops;
VisCAM/SolidView and Materialise Magics facet colours as plain
materials; Z-up turned to the model's Y-up; faceted normals from the
winding). Truncated, empty or non-finite input is an error, never a
crash. .stl is now a model extension for import, probing, the Media
Browser, the import dialog and the system report.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

docs/gaps.md

@@ -69,7 +69,7 @@ are grouped by area; the issue tracker has the rest.
 | 10 | **Colour pipeline differences** | #494 32-bpc blend modes clamp and apply opacity differently; #495 no Working Gamma 2.4; #340 ProRes 4444 tagged bt709 but sRGB-encoded; ACES 2.0 / OCIO 2.5 configs (26.5) missing; #546 / #547 viewer colour | Wrong colour in delivery is a client-visible failure | 15–30 h | G1 · [file-format-parity.md](file-format-parity.md) |
 | 11 | **Text rendering and layout** | #453 CJK text in comps, #316 paragraph alignment inverted, #483 squeezed at 4:3, #417 soft at Fit, #583 font search, #550 toolbar font options | Text is in almost every motion graphic | 10–20 h | G2 · [ui-parity.md](ui-parity.md) |
 | 12 | **3D interaction and depth** | No 3D transform gizmos (#392, #347); Z position (#489); camera aperture (#260); reflections (#261); bevel options (#315); 3D issue reopened (#307) | Advanced 3D is After Effects' growth area since 2023 | 20–35 h | G2 · [ui-parity.md](ui-parity.md) |
-| 13 | **3D model formats and materials** | After Effects 26 imports FBX, USD/USDZ, STL besides glTF and OBJ (`usd_plugins`), and Substance 3D materials with mesh displacement (26.0–26.2); we read glTF and OBJ | Product shots and 3D scenes come as FBX/USDZ | 25–45 h | — · [file-format-parity.md](file-format-parity.md) |
+| 13 | **3D model formats and materials** | After Effects 26 imports FBX, USD/USDZ, STL besides glTF and OBJ (`usd_plugins`), and Substance 3D materials with mesh displacement (26.0–26.2); we read glTF, OBJ and STL (binary and ASCII, with facet colours), not FBX, USD/USDZ or Substance | Product shots and 3D scenes come as FBX/USDZ | 25–45 h | — · [file-format-parity.md](file-format-parity.md) |
 | 14 | **Object Matte** (26.2, disk cache in 26.5) | Not present; MobileSAM is already in `effectcraft-segment` and could back it | The new one-click roto; Roto Brush covers part of it | 15–30 h | G7 · [target-app-parity.md](target-app-parity.md) |
 | 15 | **Hardware video decode and encode** | No VideoToolbox, NVENC, Quick Sync or VA-API; #498 asks for it; FilmCraft has VideoToolbox / NVENC / VA-API paths to borrow | 4K playback and export speed | 25–45 h | G5/G6 · [hardware-parity.md](hardware-parity.md) |
 | 16 | **Localization depth** | Menus in 6 languages; panels in 4; effect names and ~1,650 effect parameter names untranslated; French, German, Korean, Italian, Russian (After Effects ships them) absent; #599 Hangul boxes on macOS | After Effects is used heavily in Japan, China, Korea, Brazil, Europe | 60–110 h + native review | G9 · [localization-parity.md](localization-parity.md) |