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/outline.sexp

@@ -0,0 +1,24 @@
+;; Outline effect - shows only edges
+(require-primitives "image")
+
+(define-effect outline
+  :params (
+    (thickness :type int :default 2 :range [1 10])
+    (threshold :type int :default 100 :range [20 300])
+    (color :type list :default (list 0 0 0)
+  )
+  (fill_mode "original"))
+  (let* ((edge-img (image:edge-detect frame (/ threshold 2) threshold))
+         (dilated (if (> thickness 1)
+                      (dilate edge-img thickness)
+                      edge-img))
+         (base (cond
+                 ((= fill_mode "original") (copy frame))
+                 ((= fill_mode "white") (make-image (image:width frame) (image:height frame) (list 255 255 255)))
+                 (else (make-image (image:width frame) (image:height frame) (list 0 0 0))))))
+    (map-pixels base
+      (lambda (x y c)
+        (let ((edge-val (luminance (pixel dilated x y))))
+          (if (> edge-val 128)
+              color
+              c))))))