Record NPC sourcing decision and crowd prototypes

CREDITS.md

@@ -21,6 +21,25 @@ using Blender. The `.blend` working sources are developer artifacts and are not
 shipped. The exported `.glb` files and baked AO maps are project assets; they do
 not embed third-party models or purchased asset packs.
 
+### Development-only research previews
+
+Two review sheets under `docs/blender_previews/` compare source candidates for
+the post-0.10.0 NPC variety work. They are development documentation and are not
+bundled with the game or its release packages. The underlying source models are
+kept outside version control.
+
+- [`sheet_npc_sources_research.jpg`](docs/blender_previews/sheet_npc_sources_research.jpg)
+  includes renders of **Quaternius Ultimate Modular Characters** (CC0 1.0,
+  <https://quaternius.com/>), **Kenney Blocky Characters 2.0** (CC0 1.0,
+  <https://kenney.nl/assets/blocky-characters>), and **CesiumMan** and
+  **RiggedFigure** (CC BY 4.0, © 2017 Cesium,
+  <https://github.com/KhronosGroup/glTF-Sample-Assets>).
+- [`sheet_npc_crowd_prototypes.jpg`](docs/blender_previews/sheet_npc_crowd_prototypes.jpg)
+  contains renders of project-owned generator prototypes.
+
+The CC-BY preview images are included only as development evidence. Any future
+shipped derivative of CesiumMan or RiggedFigure must keep the attribution above.
+
 The venue geometry is authored procedurally in `src/game/world_builder.gd` as a
 stylized reconstruction. The Joke Shop is a fictional stand-in for the real
 Sunset Strip block; the game does not claim endorsement by, or an exact replica