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-effects.sexp

@@ -0,0 +1,22 @@
+;; Standard Effects Bundle
+;;
+;; Loads commonly-used video effects.
+;; Include after primitives are loaded.
+;;
+;; Effects provided:
+;;   - rotate: rotation by angle
+;;   - zoom: scale in/out
+;;   - blend: alpha blend two frames
+;;   - ripple: water ripple distortion
+;;   - invert: color inversion
+;;   - hue_shift: hue rotation
+;;
+;; Usage:
+;;   (include :path "../templates/standard-effects.sexp")
+
+(effect rotate :path "../sexp_effects/effects/rotate.sexp")
+(effect zoom :path "../sexp_effects/effects/zoom.sexp")
+(effect blend :path "../sexp_effects/effects/blend.sexp")
+(effect ripple :path "../sexp_effects/effects/ripple.sexp")
+(effect invert :path "../sexp_effects/effects/invert.sexp")
+(effect hue_shift :path "../sexp_effects/effects/hue_shift.sexp")