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/templates/standard-primitives.sexp

@@ -0,0 +1,14 @@
+;; Standard Primitives Bundle
+;;
+;; Loads all commonly-used primitive libraries.
+;; Include this at the top of streaming recipes.
+;;
+;; Usage:
+;;   (include :path "../templates/standard-primitives.sexp")
+
+(require-primitives "geometry")
+(require-primitives "core")
+(require-primitives "image")
+(require-primitives "blending")
+(require-primitives "color_ops")
+(require-primitives "streaming")