Add ascii_dual_blend recipe and fix blend/layer effects

- Add ascii_dual_blend.sexp: blends two ASCII-processed videos synced to audio
- Fix blend.sexp: add require-primitives, fix params syntax
- Fix layer.sexp: add require-primitives
- Use consistent (effect blend ...) syntax instead of special form

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

effects/ascii_dual_blend.sexp

@@ -0,0 +1,101 @@
+;; ASCII Dual Blend
+;;
+;; Applies ASCII alternating rotation effect to two video sources,
+;; blends them together, and muxes with audio.
+;; All synced to the same audio analysis.
+
+(recipe "ascii_dual_blend"
+  :version "1.0"
+  :description "Blend two ASCII-processed videos synced to audio"
+  :minimal-primitives true
+  :encoding (:codec "libx264" :crf 20 :preset "medium" :audio-codec "aac" :fps 30)
+
+  :params (
+    (cols :type int :default 50 :range [20 100]
+      :desc "Number of character columns")
+    (rotation_scale :type float :default 60 :range [0 180]
+      :desc "Max rotation in degrees")
+    (blend_opacity :type float :default 0.5 :range [0 1]
+      :desc "Blend opacity (0=video-a only, 1=video-b only)")
+    (blend_mode :type string :default "overlay"
+      :desc "Blend mode: alpha, add, multiply, screen, overlay, difference")
+    (audio_start :type float :default 60
+      :desc "Start time in audio (seconds)")
+    (duration :type float :default 10
+      :desc "Duration (seconds)")
+  )
+
+  ;; Registry - effects and analyzers
+  (effect ascii_fx_zone :path "../sexp_effects/effects/ascii_fx_zone.sexp")
+  (effect rotate :path "../sexp_effects/effects/rotate.sexp")
+  (effect blend :path "../sexp_effects/effects/blend.sexp")
+  (analyzer energy :path "../../artdag-analyzers/energy/analyzer.py")
+
+  ;; Source files
+  (def video-a (source :path "../monday.webm"))
+  (def video-b (source :path "../new.webm"))
+  (def audio (source :path "../dizzy.mp3"))
+
+  ;; Stage 1: Analysis
+  (stage :analyze
+    :outputs [energy-data]
+    (def audio-clip (-> audio (segment :start audio_start :duration duration)))
+    (def energy-data (-> audio-clip (analyze energy))))
+
+  ;; Stage 2: Process both videos
+  (stage :process
+    :requires [:analyze]
+    :inputs [energy-data]
+    :outputs [blended audio-clip]
+
+    ;; Get audio clip for final mux
+    (def audio-clip (-> audio (segment :start audio_start :duration duration)))
+
+    ;; Process video A with ASCII effect
+    (def clip-a (-> video-a (segment :start 0 :duration duration)))
+    (def ascii-a (-> clip-a
+      (effect ascii_fx_zone
+        :cols cols
+        :char_size (bind energy-data values :range [10 20])
+        :color_mode "color"
+        :background "black"
+        :energy (bind energy-data values :range [0 1])
+        :rotation_scale rotation_scale
+        :cell_effect (lambda [cell zone]
+          (rotate cell
+            (* (if (= (mod (+ (get zone "row") (get zone "col")) 2) 0) 1 -1)
+               (* (get zone "energy")
+                  (get zone "rotation_scale")
+                  (* 1.5 (+ (get zone "col-norm")
+                            (- 1 (get zone "row-norm")))))))))))
+
+    ;; Process video B with ASCII effect
+    (def clip-b (-> video-b (segment :start 0 :duration duration)))
+    (def ascii-b (-> clip-b
+      (effect ascii_fx_zone
+        :cols cols
+        :char_size (bind energy-data values :range [10 20])
+        :color_mode "color"
+        :background "black"
+        :energy (bind energy-data values :range [0 1])
+        :rotation_scale rotation_scale
+        :cell_effect (lambda [cell zone]
+          (rotate cell
+            (* (if (= (mod (+ (get zone "row") (get zone "col")) 2) 0) 1 -1)
+               (* (get zone "energy")
+                  (get zone "rotation_scale")
+                  (* 1.5 (+ (get zone "col-norm")
+                            (- 1 (get zone "row-norm")))))))))))
+
+    ;; Blend the two ASCII videos using consistent effect syntax
+    (def blended (-> ascii-a
+      (effect blend ascii-b
+        :mode blend_mode
+        :opacity blend_opacity
+        :resize_mode "fit"))))
+
+  ;; Stage 3: Output
+  (stage :output
+    :requires [:process]
+    :inputs [blended audio-clip]
+    (mux blended audio-clip)))