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>

tasks/__init__.py

@@ -1,26 +1,10 @@
-# art-celery/tasks - Celery tasks for 3-phase execution
+# art-celery/tasks - Celery tasks for streaming video rendering
 #
-# Tasks for the Art DAG distributed execution system:
-# 1. analyze_input - Extract features from input media
-# 2. execute_step - Execute a single step from the plan
-# 3. run_plan - Orchestrate execution of a full plan
-#
-# S-expression tasks:
-# 4. execute_step_sexp - Execute step from S-expression
-# 5. run_plan_sexp - Run plan from S-expression
+# Tasks:
+# 1. run_stream - Execute a streaming S-expression recipe
 
-from .analyze import analyze_input, analyze_inputs
-from .execute import execute_step
-from .orchestrate import run_plan, run_recipe
-from .execute_sexp import execute_step_sexp, run_plan_sexp
+from .streaming import run_stream
 
 __all__ = [
-    "analyze_input",
-    "analyze_inputs",
-    "execute_step",
-    "run_plan",
-    "run_recipe",
-    # S-expression tasks
-    "execute_step_sexp",
-    "run_plan_sexp",
+    "run_stream",
 ]