refactor(xcf_stack): use explicit inputs for layer list and scheduling

Replace prior_steps and runs_last with inputs=[...] step refs so GIMP
export waits only on listed layers. Add rezepttest pipeline and
bokeh-oktagon recipe.

Co-authored-by: Cursor <cursoragent@cursor.com>

pipelines/pipeline_rezepttest.py

@@ -0,0 +1,101 @@
+#!/usr/bin/env python3
+"""Rezepttest pipeline — RECIPES.md smoke test (Indians Aichelberg logo colors)."""
+
+from pathlib import Path
+
+from imagepipeline import Pipeline
+
+# Change to your Darktable export folder.
+INPUT = Path("/home/frank/tmp/bar")
+OUTPUT_BASE = Path.home() / "pipeline_output"
+
+EXISTING_OUTPUTS: dict[str, Path] = {}
+CONTINUE_FROM: Path | None = None
+
+# Colors from Indians Aichelberg logo (orange text + red stitching).
+COLOR1 = "#f0b020"  # 240, 176, 32
+COLOR2 = "#f01000"  # 240, 16, 0
+
+ALPHA1 = 160
+ALPHA2 = 110
+
+GMIC_DROP_SHADOW = "-fx_drop_shadow3d 0,0,0,10,1,1,2,0.5,240,16,0,200,0"
+GMIC_JPR_SMOOTH = "-jpr_gradient_smooth 0,1.5"
+GMIC_BOKEH = (
+    f"-fx_bokeh 3,5,0,30,8,4,0.3,0.2,240,176,32,{ALPHA1},0.7,30,20,20,1,2,"
+    f"240,16,0,{ALPHA2},0.15"
+)
+
+
+def main() -> None:
+    with Pipeline(
+        name="rezepttest",
+        input_dir=INPUT,
+        output_base=OUTPUT_BASE,
+        existing_outputs=EXISTING_OUTPUTS or None,
+        continue_from=CONTINUE_FROM,
+    ) as p:
+        rembg_out = p.step("rembg", inputs="input")
+        grayscale = p.step("gmic_grayscale", inputs="input")
+        gradient_radial_bg = p.step(
+            "imagemagick_fill",
+            inputs="input",
+            color1=COLOR1,
+            color2=COLOR2,
+            gradient=True,
+            radial=True,
+        )
+
+        rembg_shadow = p.step("gmic", inputs=rembg_out, command=GMIC_DROP_SHADOW)
+        rembg_jpr_smooth = p.step("gmic", inputs=rembg_out, command=GMIC_JPR_SMOOTH)
+        rembg_jpr_smooth_sized = p.step(
+            "imagemagick_scale_crop",
+            inputs=rembg_jpr_smooth,
+            scale=1.05,
+        )
+        input_bokeh = p.step("gmic", inputs="input", command=GMIC_BOKEH)
+
+        # recipe: colorsplash
+        composite_colorsplash = p.step("composite", inputs=[grayscale, rembg_out])
+
+        # recipe: rembg-radial-2colors (gradient-radial)
+        composite_radial = p.step("composite", inputs=[gradient_radial_bg, rembg_out])
+
+        # recipe: original-drop-shadow-rembg
+        shadow_mid = p.step("composite", inputs=["input", rembg_shadow])
+        composite_shadow = p.step("composite", inputs=[shadow_mid, rembg_out])
+
+        # recipe: original-jpr-smooth-rembg
+        smooth_mid = p.step("composite", inputs=["input", rembg_jpr_smooth_sized])
+        composite_smooth = p.step("composite", inputs=[smooth_mid, rembg_out])
+
+        # recipe: bokeh-oktagon
+        bokeh_mid = p.step("composite", inputs=["input", input_bokeh])
+        composite_bokeh = p.step("composite", inputs=[bokeh_mid, rembg_out])
+
+        # recipe: xcf-stack — explicit layer list, bottom to top
+        p.step(
+            "xcf_stack",
+            inputs=[
+                "input",
+                rembg_out,
+                grayscale,
+                gradient_radial_bg,
+                rembg_shadow,
+                rembg_jpr_smooth_sized,
+                input_bokeh,
+                composite_colorsplash,
+                composite_radial,
+                composite_shadow,
+                composite_smooth,
+                composite_bokeh,
+            ],
+        )
+
+        output_root = p.run()
+
+    print(f"Pipeline finished. Output: {output_root}")
+
+
+if __name__ == "__main__":
+    main()