data(assets): promote the four spike GLBs — first production environment assets (T-1204)

table_baroque, chair_modernist, desk_scifi (furniture, with mask
sidecars) and lion_statue (props, non-tintable) enter
client/assets/models/ under the category-first convention, byte-
identical to the spike sources (MD5-verified; spikes/ untouched,
vw_beetle excluded per the Q-067 deferral). Postprocess verified
already-applied by Blender node-graph inspection (mat_primary,
roughness=1.0/specular=0.0 shader inputs — the convenience properties
read stale defaults, the graph is authoritative), so not re-run. All
four registered in manifest.json at 'planned' with footprint_tiles
[1,1] (a flagged judgment call — normalized spike geometry erases
real-world scale; the brief ruling goes to araminta in review).
In-engine proof: clean headless import + ResourceLoader load +
instantiate for all four. Discovery documented in conventions.md §2 +
glb-gen SKILL.md: Godot externalizes the GLB's embedded texture as a
<model>_Image_0.png sidecar referenced by binary UID — it must be
committed or loading breaks with an undiscoverable dependency error.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

docs/assets/visual/conventions.md

@@ -65,6 +65,27 @@ correction). This is the same mechanism, not a parallel one: environment
 props reuse the clothing pipeline's multi-region shader family rather than
 inventing a props-specific one.
 
+**Extracted-texture sidecar (`_Image_0.png`) — generated, must be committed.**
+On first Godot import of a promoted `.glb`, the scene importer externalizes
+the model's embedded texture to a loose file next to it,
+`<model>_Image_0.png` (e.g. `table_baroque_Image_0.png`), and the compiled
+`.godot/imported/*.scn` references that file by **UID**, as an external
+dependency — this happens even with `gltf/embedded_image_handling=3` (embed
+uncompressed) set in `project.godot`, confirmed on Godot 4.6 (T-1204
+promotion). This file is **machine-generated, never hand-edited** — if it is
+lost or deleted, a clean re-import (delete the stale `.glb.import` +
+`.godot/imported/*.scn` cache entry, then re-run `godot4 --headless --import`)
+regenerates it deterministically. But it **must be committed alongside the
+`.glb`** it belongs to: deleting it after import breaks loading with
+`ERROR: Can't load dependency` / `Resource file not found` at `ResourceLoader`
+time, and critically, **a text grep of the compiled `.scn` will not reveal
+this dependency** — the reference is a binary-encoded UID (`uid://...`), not
+a literal path string, so searching the `.scn` for the filename finds
+nothing. Losing this file costs a full debug cycle (re-copy the source `.glb`,
+clear the stale `.import`/`.scn` cache, re-import, re-verify) to rediscover
+what the UID reference actually pointed to — treat it as a required sidecar
+from the moment of promotion, not disposable import cache.
+
 ---
 
 ## 3. Texture naming (D-235 tokens)