Initial commit: video effects processing system

Add S-expression based video effects pipeline with modular effect
definitions, constructs, and recipe files.

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

recipe-lambda.sexp

@@ -0,0 +1,28 @@
+; Beat-synced video recipe with lambda reducer
+(recipe "beat-sync-lambda"
+  :version "1.0"
+  :encoding (:codec "libx264" :crf 22 :preset "fast" :audio-codec "aac")
+
+  ; Declare analyzers and effects
+  (analyzer beats :path "../artdag-analyzers/beats/analyzer.py")
+  (effect invert :path "../artdag-effects/invert/effect.py")
+
+  ; Sources
+  (def video (source :path "new.webm" :description "Video input"))
+  (def audio (-> (source :path "dizzy.mp3" :description "Audio input")
+                 (segment :start 0 :duration 10)))
+
+  ; Analyze audio for beats
+  (def analysis (-> audio (analyze beats)))
+
+  ; Slice video at beat times using lambda reducer
+  (def synced-video (slice-on video analysis
+                      :times times
+                      :init 0
+                      :fn (fn [acc i start end]
+                            {:source video
+                             :effects (if (odd? i) (list invert) (list))
+                             :acc (inc acc)})))
+
+  ; Mux video with audio
+  (mux synced-video audio))