feat(sequence): Clean up compiler and add test accessor

- Remove debug output from seq_compiler_v2.py
- Add get_effect_dag() accessor for testing
- Add e2e test skeleton (shader compatibility pending)

handoff(Claude): v2 foundation complete, 3 phases done

3 files changed, 14 insertions, 10 deletions

diff --git a/cmake/DemoTests.cmake b/cmake/DemoTests.cmake
index 3e54ea2..2f7cdd1 100644
--- a/cmake/DemoTests.cmake
+++ b/cmake/DemoTests.cmake
@@ -243,6 +243,15 @@ add_demo_test(test_sequence_v2 SequenceV2Test gpu
 target_link_libraries(test_sequence_v2 PRIVATE 3d gpu audio procedural util ${DEMO_LIBS})
 demo_add_asset_deps(test_sequence_v2 shaders)
 
+# Sequence v2 End-to-End Test
+add_demo_test(test_sequence_v2_e2e SequenceV2E2ETest gpu
+    src/tests/gpu/test_sequence_v2_e2e.cc
+    src/tests/common/webgpu_test_fixture.cc
+    ${PLATFORM_SOURCES}
+    ${GEN_DEMO_CC})
+target_link_libraries(test_sequence_v2_e2e PRIVATE 3d gpu audio procedural util ${DEMO_LIBS})
+demo_add_asset_deps(test_sequence_v2_e2e shaders)
+
 # Subsystem test targets
 add_custom_target(run_audio_tests
     COMMAND ${CMAKE_CTEST_COMMAND} -L audio --output-on-failure
diff --git a/src/gpu/sequence_v2.h b/src/gpu/sequence_v2.h
index 9cd93c6..1cc5f47 100644
--- a/src/gpu/sequence_v2.h
+++ b/src/gpu/sequence_v2.h
@@ -96,6 +96,11 @@ class SequenceV2 {
 
   void resize(int width, int height);
 
+  // Test accessor
+  const std::vector<EffectDAGNode>& get_effect_dag() const {
+    return effect_dag_;
+  }
+
  protected:
   const GpuContext& ctx_;
   int width_;
diff --git a/tools/seq_compiler_v2.py b/tools/seq_compiler_v2.py
index 56bf613..6ae6283 100755
--- a/tools/seq_compiler_v2.py
+++ b/tools/seq_compiler_v2.py
@@ -332,8 +332,6 @@ def detect_ping_pong(seq: SequenceDecl, sorted_effects: List[EffectDecl]) -> Dic
         eff1 = sorted_effects[i]
         eff2 = sorted_effects[i + 1]
 
-        print(f"DEBUG: Checking pair {i}: {eff1.class_name}({eff1.inputs}->{eff1.outputs}) and {eff2.class_name}({eff2.inputs}->{eff2.outputs})", file=sys.stderr)
-
         # Find nodes that alternate
         for out1 in eff1.outputs:
             if out1 in ['source', 'sink'] or out1 in used_nodes:
@@ -343,32 +341,24 @@ def detect_ping_pong(seq: SequenceDecl, sorted_effects: List[EffectDecl]) -> Dic
                 if in1 in ['source', 'sink'] or in1 in used_nodes:
                     continue
 
-                print(f"DEBUG: Testing out1={out1}, in1={in1}: in1 in eff2.outputs={in1 in eff2.outputs}, out1 in eff2.inputs={out1 in eff2.inputs}", file=sys.stderr)
-
                 # Check if eff2 writes in1 and reads out1 (alternating)
                 if in1 in eff2.outputs and out1 in eff2.inputs:
                     # Classic ping-pong: eff1 (reads in1, writes out1), eff2 (reads out1, writes in1)
-                    print(f"DEBUG: Found potential ping-pong: {in1} <-> {out1} between {eff1.class_name} and {eff2.class_name}", file=sys.stderr)
-
                     # Check no other effects use these nodes
                     other_uses = False
                     for j, eff in enumerate(sorted_effects):
                         if j == i or j == i + 1:
                             continue
                         if out1 in eff.inputs + eff.outputs or in1 in eff.inputs + eff.outputs:
-                            print(f"DEBUG: Other effect {eff.class_name} uses {out1 if out1 in eff.inputs + eff.outputs else in1}", file=sys.stderr)
                             other_uses = True
                             break
 
                     if not other_uses:
-                        print(f"DEBUG: Aliasing {in1} -> {out1}", file=sys.stderr)
                         # Alias in1 -> out1 (in1 uses same texture as out1)
                         aliases[in1] = out1
                         used_nodes.add(out1)
                         used_nodes.add(in1)
                         break
-                    else:
-                        print(f"DEBUG: Skipping alias due to other uses", file=sys.stderr)
 
     return aliases