Replace batch DAG system with streaming architecture

- Remove legacy_tasks.py, hybrid_state.py, render.py
- Remove old task modules (analyze, execute, execute_sexp, orchestrate)
- Add streaming interpreter from test repo
- Add sexp_effects with primitives and video effects
- Add streaming Celery task with CID-based asset resolution
- Support both CID and friendly name references for assets
- Add .dockerignore to prevent local clones from conflicting

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

sexp_effects/effects/ascii_art.sexp

@@ -0,0 +1,17 @@
+;; ASCII Art effect - converts image to ASCII characters
+(require-primitives "ascii")
+
+(define-effect ascii_art
+  :params (
+    (char_size :type int :default 8 :range [4 32])
+    (alphabet :type string :default "standard")
+    (color_mode :type string :default "color" :desc ""color", "mono", "invert", or any color name/hex")
+    (background_color :type string :default "black" :desc "background color name/hex")
+    (invert_colors :type int :default 0 :desc "swap foreground and background colors")
+    (contrast :type float :default 1.5 :range [1 3])
+  )
+  (let* ((sample (cell-sample frame char_size))
+         (colors (nth sample 0))
+         (luminances (nth sample 1))
+         (chars (luminance-to-chars luminances alphabet contrast)))
+    (render-char-grid frame chars colors char_size color_mode background_color invert_colors)))