Shade sprite module: faction generation, asset scanning, TextureCache

Extends the shade_sprite module (for merchant-shade.itch.io character
sprite sheets) with procedural faction generation and asset management:

- FactionGenerator: seed-based faction recipes with Biome, Element,
  Aesthetic, and RoleType enums for thematic variety
- AssetLibrary: filesystem scanner that discovers and categorizes
  layer PNGs by type (skins, clothes, hair, etc.)
- TextureCache: avoids redundant disk I/O when building many variants
- CharacterAssembler: HSL shift documentation, method improvements
- Demo expanded to 6 interactive scenes (animation viewer, HSL recolor,
  character gallery, faction generator, layer compositing, equipment)
- EVALUATION.md: 7DRL readiness assessment of the full module
- 329-line faction generation test suite

Assets themselves are not included -- sprite sheets are external
dependencies, some under commercial license.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

shade_sprite/__init__.py

@@ -29,6 +29,14 @@ For layered characters:
     assembler.add_layer("clothes/BasicBlue-Body.png", hue_shift=120.0)
     assembler.add_layer("hair/M-Hairstyle1-Black.png")
     texture = assembler.build("my_character")
+
+For procedural factions:
+    from shade_sprite import FactionGenerator, AssetLibrary
+
+    lib = AssetLibrary()
+    gen = FactionGenerator(seed=42, library=lib)
+    recipe = gen.generate()
+    textures = recipe.build_role_textures(assembler)
 """
 
 from .formats import (
@@ -44,12 +52,23 @@ from .formats import (
     detect_format,
 )
 from .animation import AnimatedSprite
-from .assembler import CharacterAssembler
+from .assembler import CharacterAssembler, TextureCache
+from .assets import AssetLibrary, LayerFile
+from .factions import (
+    FactionRecipe,
+    FactionGenerator,
+    RoleDefinition,
+    Biome,
+    Element,
+    Aesthetic,
+    RoleType,
+)
 
 __all__ = [
     # Core classes
     "AnimatedSprite",
     "CharacterAssembler",
+    "TextureCache",
     # Format definitions
     "Direction",
     "AnimFrame",
@@ -63,4 +82,15 @@ __all__ = [
     "ALL_FORMATS",
     # Utilities
     "detect_format",
+    # Asset scanning
+    "AssetLibrary",
+    "LayerFile",
+    # Faction generation
+    "FactionRecipe",
+    "FactionGenerator",
+    "RoleDefinition",
+    "Biome",
+    "Element",
+    "Aesthetic",
+    "RoleType",
 ]