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>

sexp_effects/effects/wave.sexp

@@ -0,0 +1,20 @@
+;; Wave effect - sine wave displacement distortion
+;; @param amplitude float [0, 100] default 10
+;; @param wavelength float [10, 500] default 50
+;; @param speed float [0, 10] default 1
+;; @param direction string default "horizontal"
+
+(define-effect wave
+  ((amplitude 10) (wavelength 50) (speed 1) (direction "horizontal"))
+  (let* ((w (width frame))
+         (h (height frame))
+         ;; Use _time for animation phase
+         (phase (* (or _time 0) speed 2 pi))
+         ;; Calculate frequency: waves per dimension
+         (freq (/ (if (= direction "vertical") w h) wavelength))
+         (axis (cond
+                 ((= direction "horizontal") "x")
+                 ((= direction "vertical") "y")
+                 (else "both")))
+         (coords (wave-displace w h axis freq amplitude phase)))
+    (remap frame (coords-x coords) (coords-y coords))))