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/fisheye.sexp

@@ -0,0 +1,14 @@
+;; Fisheye effect - barrel/pincushion lens distortion
+;; @param strength float [-1, 1] default 0.3
+;; @param center_x float [0, 1] default 0.5
+;; @param center_y float [0, 1] default 0.5
+;; @param zoom_correct bool default true
+
+(define-effect fisheye
+  ((strength 0.3) (center_x 0.5) (center_y 0.5) (zoom_correct true))
+  (let* ((w (width frame))
+         (h (height frame))
+         (cx (* w center_x))
+         (cy (* h center_y))
+         (coords (fisheye-displace w h strength cx cy zoom_correct)))
+    (remap frame (coords-x coords) (coords-y coords))))