test(comfyui): tests offline para 15 builders/funciones puras sin test

Cubre 15 funciones del grupo comfyui (+ las 4 de comfyui-judge) que no tenian
test, con tests offline (sin red, sin GPU, sin servidor ComfyUI):

- 5 builders puros gamedev-2d: build_asset_variant, build_directional_sprite,
  build_inpaint_asset, build_outpaint_asset, build_sprite_from_sketch (estructura
  del workflow en API format + cableado + determinismo + error paths).
- 3 impuras offline via PIL/stdlib: build_grid, flatten_alpha_on_color,
  read_png_metadata (PNGs reales en tmp, error paths).
- 4 de comfyui-judge: score_aesthetic y score_clip_alignment por sus guards
  previos al subproceso torch; judge_image (panel) y critique_image_llm con la
  dependencia pesada monkeypatcheada.
- 3 que componen otras funciones: resolve_workflow_deps, import_workflow_json,
  extract_recipe_from_png (dependencia de red monkeypatcheada o fallback offline).

Cada .md actualizado con tested: true + test_file_path + tests.
Cobertura del grupo comfyui (tag plano): 79 -> 90 con test (47 -> 36 sin).
comfyui-judge: 0/4 -> 4/4. pytest: 101 passed; carpeta ml/tests: 376 passed.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

python/functions/ml/comfyui_read_png_metadata.md

@@ -18,9 +18,9 @@ params:
   - name: png_path
     desc: "Ruta local del PNG generado por ComfyUI."
 output: "dict {ok, prompt, parameters, error}. prompt = workflow API format embebido (dict); parameters = {model, seed, steps, cfg, sampler_name, scheduler, denoise, positive, negative} extraido del KSampler y nodos conectados; error = motivo si ok=False."
-tested: false
-tests: []
-test_file_path: ""
+tested: true
+tests: ["extrae prompt embebido + parametros del KSampler (seed/steps/cfg/sampler/scheduler/denoise/positive/negative/model)", "error: archivo inexistente", "error: PNG sin chunk prompt", "error: chunk prompt no es JSON", "error: no es un PNG valido", "determinismo"]
+test_file_path: "python/functions/ml/tests/test_comfyui_read_png_metadata.py"
 file_path: "python/functions/ml/comfyui_read_png_metadata.py"
 ---