Phase 1: s-expression core library + test infrastructure

S-expression parser, evaluator, and primitive registry in shared/sexp/.
109 unit tests covering parsing, evaluation, special forms, lambdas,
closures, components (defcomp), and 60+ pure builtins.

Test infrastructure: Dockerfile.unit (tier 1, fast) and
Dockerfile.integration (tier 2, ffmpeg). Dev watch mode auto-reruns
on file changes. Deploy gate blocks push on test failure.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

docker-compose.dev.yml

@@ -335,6 +335,41 @@ services:
       - ./account/__init__.py:/app/account/__init__.py:ro
       - ./account/models:/app/account/models:ro
 
+  test-unit:
+    build:
+      context: .
+      dockerfile: test/Dockerfile.unit
+    volumes:
+      - ./shared:/app/shared
+      - ./artdag/core:/app/artdag/core
+      - ./artdag/l1/tests:/app/artdag/l1/tests
+      - ./artdag/l1/sexp_effects:/app/artdag/l1/sexp_effects
+      - ./artdag/l1/app:/app/artdag/l1/app
+    entrypoint: >
+      python -m pytest_watch
+      --runner "python -m pytest -v --tb=short"
+      --
+      shared/
+      artdag/core/tests/
+      artdag/core/artdag/sexp/
+      artdag/l1/tests/
+      artdag/l1/sexp_effects/
+      --ignore=artdag/l1/tests/test_jax_primitives.py
+      --ignore=artdag/l1/tests/test_jax_pipeline_integration.py
+      -k "not gpu and not cuda"
+    profiles:
+      - test
+
+  test-integration:
+    build:
+      context: .
+      dockerfile: test/Dockerfile.integration
+    volumes:
+      - ./shared:/app/shared
+      - ./artdag:/app/artdag
+    profiles:
+      - test
+
 networks:
   appnet:
     driver: bridge