feat(sprite-generation): ✨ Add experimental sprite generation scripts and configs in the experiments directory to enable advanced image optimization workflows

Co-Authored-By: Lilith Autocommit <noreply@atlilith.com>

tools/sprite-generation/experiments/2026-03-27_model_comparison.yaml

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+# Model Comparison Experiments — 2026-03-27
+# Testing which SDXL model produces game-ready unit sprites
+# Target: overhead isometric, green chroma key, painted fantasy style, southwest-facing
+
+experiment: model_comparison
+date: 2026-03-27
+sprite: spearmen_dwarves_f
+prompt_version: "YAML-driven v1 (unit_classes.yaml + composition.yaml)"
+
+models:
+  juggernaut-xl-v9:
+    full_name: "Juggernaut-XL_v9_RunDiffusionPhoto_v2"
+    file_size_gb: 6.9
+    vram_mb: ~8500
+    sdxl_base: true
+    results:
+      total_generated: 18
+      gates_passed: 0
+      common_failures:
+        - "facing_southwest: always faces camera or forward"
+        - "no_shadow: always renders cast shadows"
+        - "no_base_or_ground: always adds ground plane"
+        - "not_photorealistic: renders 3D photorealistic (it's a PHOTO model)"
+        - "green_background: produces blue/purple/teal backgrounds"
+      strengths:
+        - "correct_subject_type: SPEAR + SHIELD always present (unit_classes.yaml works)"
+        - "anti-green-bleed: copper/brown/silver armor (NON-GREEN directive works)"
+      verdict: "REJECT — fundamentally a photorealistic model, can't produce painted game art"
+      note: "Name literally says 'RunDiffusionPhoto' — wrong model for stylized game art"
+
+  juggernaut-xi-v11:
+    full_name: "Juggernaut-XI-byRunDiffusion"
+    file_size_gb: 7.1
+    vram_mb: ~9000
+    sdxl_base: true
+    results:
+      total_generated: "~800 (across many prompt iterations)"
+      common_failures:
+        - "facing_southwest: ~50% hit rate (SDXL limitation)"
+        - "no_shadow: sometimes renders shadows (improved with negative)"
+        - "green armor bleed: characters pick up green from chroma background"
+      strengths:
+        - "Produces painted/stylized art when prompted correctly"
+        - "Responds to 'close-up isometric view from above'"
+        - "Green chroma key background works ~70% of time"
+        - "Better at non-photorealistic styles than v9"
+      verdict: "CURRENT BEST — not perfect but produces usable painted art"
+      note: "Earlier loading crash was VRAM contention, not model issue"
+
+  # Models NOT YET TESTED (available in model-boss manifest):
+  epicrealism-xl:
+    status: untested
+    notes: "Realism-focused, likely similar issues to v9"
+
+  illustrious-xl-v2:
+    status: untested
+    notes: "Anime/illustration focused — CLAUDE.md says NEVER use anime models"
+
+# Key findings:
+# 1. SDXL models with "Photo" in name can't produce painted game art
+# 2. SDXL can't reliably control facing direction (~50% southwest hit rate)
+# 3. Green chroma key causes color bleed onto subject — anti-bleed negatives help
+# 4. Unit class weapon descriptions (SPEAR, LONGBOW) work well when placed early in prompt
+# 5. v11 is the right model but needs model-boss VRAM stability to load reliably