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/swirl.sexp

@@ -0,0 +1,17 @@
+;; Swirl effect - spiral vortex distortion
+(require-primitives "geometry" "image")
+
+(define-effect swirl
+  :params (
+    (strength :type int :default 1 :range [-10 10])
+    (radius :type float :default 0.5 :range [0.1 2])
+    (center_x :type float :default 0.5 :range [0 1])
+    (center_y :type float :default 0.5 :range [0 1])
+    (falloff :type string :default "quadratic")
+  )
+  (let* ((w (image:width frame))
+         (h (image:height frame))
+         (cx (* w center_x))
+         (cy (* h center_y))
+         (coords (geometry:swirl-coords w h strength radius cx cy falloff)))
+    (geometry:remap frame (geometry:coords-x coords) (geometry:coords-y coords))))