Incorporate art-dag-mono repo into artdag/ subfolder

Merges full history from art-dag/mono.git into the monorepo
under the artdag/ directory. Contains: core (DAG engine),
l1 (Celery rendering server), l2 (ActivityPub registry),
common (shared templates/middleware), client (CLI), test (e2e).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

git-subtree-dir: artdag
git-subtree-mainline: 1a179de547
git-subtree-split: 4c2e716558

artdag/test/sexp_effects/effects/wave.sexp

@@ -0,0 +1,22 @@
+;; Wave effect - sine wave displacement distortion
+(require-primitives "geometry" "image")
+
+(define-effect wave
+  :params (
+    (amplitude :type int :default 10 :range [0 100])
+    (wavelength :type int :default 50 :range [10 500])
+    (speed :type int :default 1 :range [0 10])
+    (direction :type string :default "horizontal")
+  )
+  (let* ((w (image:width frame))
+         (h (image: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 (geometry:wave-coords w h axis freq amplitude phase)))
+    (geometry:remap frame (geometry:coords-x coords) (geometry:coords-y coords))))