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/l1/sexp_effects/effects/ascii_zones.sexp

@@ -0,0 +1,30 @@
+;; ASCII Zones effect - different character sets for different brightness zones
+;; Dark areas use simple chars, mid uses standard, bright uses blocks
+(require-primitives "ascii")
+
+(define-effect ascii_zones
+  :params (
+    (char_size :type int :default 8 :range [4 32])
+    (dark_threshold :type int :default 80 :range [0 128])
+    (bright_threshold :type int :default 180 :range [128 255])
+    (color_mode :type string :default "color")
+  )
+  (let* ((sample (cell-sample frame char_size))
+         (colors (nth sample 0))
+         (luminances (nth sample 1))
+         ;; Start with simple chars as base
+         (base-chars (luminance-to-chars luminances "simple" 1.2))
+         ;; Map each cell to appropriate alphabet based on brightness zone
+         (zoned-chars (map-char-grid base-chars luminances
+                        (lambda (r c ch lum)
+                          (cond
+                            ;; Bright zones: use block characters
+                            ((> lum bright_threshold)
+                             (alphabet-char "blocks" (floor (/ (- lum bright_threshold) 15))))
+                            ;; Dark zones: use simple sparse chars
+                            ((< lum dark_threshold)
+                             (alphabet-char " .-" (floor (/ lum 30))))
+                            ;; Mid zones: use standard ASCII
+                            (else
+                             (alphabet-char "standard" (floor (/ lum 4)))))))))
+    (render-char-grid frame zoned-chars colors char_size color_mode (list 0 0 0))))