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/ripple.sexp

@@ -0,0 +1,17 @@
+;; Ripple effect - radial wave distortion from center
+;; @param frequency float [1, 20] default 5
+;; @param amplitude float [0, 50] default 10
+;; @param center_x float [0, 1] default 0.5
+;; @param center_y float [0, 1] default 0.5
+;; @param decay float [0, 5] default 1
+;; @param speed float [0, 10] default 1
+
+(define-effect ripple
+  ((frequency 5) (amplitude 10) (center_x 0.5) (center_y 0.5) (decay 1) (speed 1))
+  (let* ((w (width frame))
+         (h (height frame))
+         (cx (* w center_x))
+         (cy (* h center_y))
+         (phase (* (or _time 0) speed 2 pi))
+         (coords (ripple-displace w h frequency amplitude cx cy decay phase)))
+    (remap frame (coords-x coords) (coords-y coords))))