feat(sequence): complete v2 migration with DAG-based routing

Phase 4 complete: V1 system removed, v2 fully operational.

Architecture Changes:
- Explicit Node system with typed buffers (u8x4_norm, f32x4, depth24)
- DAG effect routing with multi-input/multi-output support
- Python compiler (seq_compiler_v2.py) with topological sort and ping-pong optimization
- Compile-time node aliasing for framebuffer reuse

V1 Removal (~4KB):
- Deleted effect.h/cc base classes (1.4KB)
- Deleted 19 v1 effect pairs: heptagon, particles, passthrough, gaussian_blur,
  solarize, scene1, chroma_aberration, vignette, hybrid_3d, flash_cube,
  theme_modulation, fade, flash, circle_mask, rotating_cube, sdf_test,
  distort, moving_ellipse, particle_spray (2.7KB)

V2 Effects Ported:
- PassthroughEffectV2, PlaceholderEffectV2
- GaussianBlurEffectV2 (multi-pass with temp nodes)
- HeptagonEffectV2 (scene effect with dummy texture)
- ParticlesEffectV2 (compute + render, format fixed)
- RotatingCubeEffectV2 (3D with depth node)
- Hybrid3DEffectV2 (Renderer3D integration, dummy textures for noise/sky)

Compiler Features:
- DAG validation (cycle detection, connectivity checks)
- Topological sort for execution order
- Ping-pong optimization (aliased node detection)
- Surface-based and encoder-based RenderV2Timeline generation
- init_effect_nodes() automatic generation

Fixes Applied:
- WebGPU binding layout validation (standard v2 post-process layout)
- Surface format mismatch (ctx.format for blit, RGBA8Unorm for framebuffers)
- Depth attachment compatibility (removed forced depth from gpu_create_render_pass)
- Renderer3D texture initialization (created dummy 1x1 white textures)
- ParticlesEffectV2 format (changed from ctx.format to RGBA8Unorm)
- Encoder-based RenderV2Timeline (added missing preprocess() call)

Testing:
- 34/36 tests passing (2 v1-dependent tests disabled)
- demo64k runs successfully (no crashes)
- All seek positions work (--seek 12, --seek 15 validated)

Documentation:
- Updated PROJECT_CONTEXT.md (v2 status, reference to SEQUENCE_v2.md)
- Added completion entry to COMPLETED.md

TODO (Future):
- Port CNN effects to v2
- Implement flatten mode (--flatten code generation)
- Port remaining 10+ effects
- Update HTML timeline editor for v2 (deferred)

handoff(Claude): Sequence v2 migration complete, v1 removed, system operational.
Phase 5 (editor) deferred per user preference.

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

1 files changed, 0 insertions, 204 deletions

diff --git a/src/effects/rotating_cube_effect.cc b/src/effects/rotating_cube_effect.cc
deleted file mode 100644
index c03eccb..0000000
--- a/src/effects/rotating_cube_effect.cc
+++ /dev/null
@@ -1,204 +0,0 @@
-// This file is part of the 64k demo project.
-// It implements RotatingCubeEffect for bump-mapped rotating cube rendering.
-// Uses auxiliary texture masking to render only inside a circular region.
-
-#include "effects/rotating_cube_effect.h"
-#include "generated/assets.h"
-#include "gpu/bind_group_builder.h"
-#include "gpu/gpu.h"
-#include "gpu/sampler_cache.h"
-#include "gpu/shader_composer.h"
-#include "util/asset_manager_utils.h"
-
-RotatingCubeEffect::RotatingCubeEffect(const GpuContext& ctx) : Effect(ctx) {
-}
-
-RotatingCubeEffect::~RotatingCubeEffect() {
-  // Samplers owned by SamplerCache - don't release
-  if (noise_view_)
-    wgpuTextureViewRelease(noise_view_);
-  if (noise_texture_)
-    wgpuTextureRelease(noise_texture_);
-  if (bind_group_1_)
-    wgpuBindGroupRelease(bind_group_1_);
-  if (bind_group_0_)
-    wgpuBindGroupRelease(bind_group_0_);
-  if (pipeline_)
-    wgpuRenderPipelineRelease(pipeline_);
-}
-
-void RotatingCubeEffect::init(MainSequence* demo) {
-  demo_ = demo;
-
-  uniform_buffer_ =
-      gpu_create_buffer(ctx_.device, sizeof(Uniforms),
-                        WGPUBufferUsage_Uniform | WGPUBufferUsage_CopyDst);
-  object_buffer_ =
-      gpu_create_buffer(ctx_.device, sizeof(ObjectData),
-                        WGPUBufferUsage_Storage | WGPUBufferUsage_CopyDst);
-
-  TextureWithView noise = gpu_create_texture_2d(
-      ctx_.device, 1, 1, WGPUTextureFormat_RGBA8Unorm,
-      (WGPUTextureUsage)(WGPUTextureUsage_TextureBinding |
-                         WGPUTextureUsage_RenderAttachment),
-      1);
-  noise_texture_ = noise.texture;
-  noise_view_ = noise.view;
-
-  noise_sampler_ =
-      SamplerCache::Get().get_or_create(ctx_.device, SamplerCache::linear());
-  mask_sampler_ =
-      SamplerCache::Get().get_or_create(ctx_.device, SamplerCache::clamp());
-
-  size_t shader_size;
-  const char* shader_code =
-      (const char*)GetAsset(AssetId::ASSET_MASKED_CUBE_SHADER, &shader_size);
-
-  ShaderComposer::CompositionMap composition_map;
-  composition_map["render/scene_query_mode"] = "render/scene_query_linear";
-  composed_shader_ = ShaderComposer::Get().Compose(
-      {}, std::string(shader_code, shader_size), composition_map);
-
-  WGPUShaderSourceWGSL wgsl_src = {};
-  wgsl_src.chain.sType = WGPUSType_ShaderSourceWGSL;
-  wgsl_src.code = str_view(composed_shader_.c_str());
-
-  WGPUShaderModuleDescriptor shader_desc = {};
-  shader_desc.nextInChain = &wgsl_src.chain;
-  WGPUShaderModule shader_module =
-      wgpuDeviceCreateShaderModule(ctx_.device, &shader_desc);
-
-  WGPUBindGroupLayout bgl_0 =
-      BindGroupLayoutBuilder()
-          .uniform(0, WGPUShaderStage_Vertex | WGPUShaderStage_Fragment,
-                   sizeof(Uniforms))
-          .storage(1, WGPUShaderStage_Vertex | WGPUShaderStage_Fragment,
-                   sizeof(ObjectData))
-          .texture(3, WGPUShaderStage_Fragment)
-          .sampler(4, WGPUShaderStage_Fragment)
-          .build(ctx_.device);
-
-  WGPUBindGroupLayout bgl_1 = BindGroupLayoutBuilder()
-                                  .texture(0, WGPUShaderStage_Fragment)
-                                  .sampler(1, WGPUShaderStage_Fragment)
-                                  .build(ctx_.device);
-
-  const WGPUBindGroupLayout bgls[] = {bgl_0, bgl_1};
-  const WGPUPipelineLayoutDescriptor pl_desc = {
-      .bindGroupLayoutCount = 2,
-      .bindGroupLayouts = bgls,
-  };
-  WGPUPipelineLayout pipeline_layout =
-      wgpuDeviceCreatePipelineLayout(ctx_.device, &pl_desc);
-
-  const WGPUColorTargetState color_target = {
-      .format = ctx_.format,
-      .writeMask = WGPUColorWriteMask_All,
-  };
-
-  const WGPUDepthStencilState depth_stencil = {
-      .format = WGPUTextureFormat_Depth24Plus,
-      .depthWriteEnabled = WGPUOptionalBool_True,
-      .depthCompare = WGPUCompareFunction_Less,
-  };
-
-  WGPUFragmentState fragment = {};
-  fragment.module = shader_module;
-  fragment.entryPoint = str_view("fs_main");
-  fragment.targetCount = 1;
-  fragment.targets = &color_target;
-
-  WGPURenderPipelineDescriptor pipeline_desc = {};
-  pipeline_desc.layout = pipeline_layout;
-  pipeline_desc.vertex.module = shader_module;
-  pipeline_desc.vertex.entryPoint = str_view("vs_main");
-  pipeline_desc.primitive.topology = WGPUPrimitiveTopology_TriangleList;
-  pipeline_desc.primitive.cullMode = WGPUCullMode_None;
-  pipeline_desc.depthStencil = &depth_stencil;
-  pipeline_desc.multisample.count = 1;
-  pipeline_desc.multisample.mask = 0xFFFFFFFF;
-  pipeline_desc.fragment = &fragment;
-
-  pipeline_ = wgpuDeviceCreateRenderPipeline(ctx_.device, &pipeline_desc);
-  wgpuShaderModuleRelease(shader_module);
-  wgpuPipelineLayoutRelease(pipeline_layout);
-
-  const WGPUBindGroupEntry entries_0[] = {
-      {.binding = 0,
-       .buffer = uniform_buffer_.buffer,
-       .size = sizeof(Uniforms)},
-      {.binding = 1,
-       .buffer = object_buffer_.buffer,
-       .size = sizeof(ObjectData)},
-      {.binding = 3, .textureView = noise_view_},
-      {.binding = 4, .sampler = noise_sampler_},
-  };
-
-  const WGPUBindGroupDescriptor bg_desc_0 = {
-      .layout = bgl_0,
-      .entryCount = 4,
-      .entries = entries_0,
-  };
-  bind_group_0_ = wgpuDeviceCreateBindGroup(ctx_.device, &bg_desc_0);
-  wgpuBindGroupLayoutRelease(bgl_0);
-
-  WGPUTextureView mask_view = demo_->get_auxiliary_view("circle_mask");
-  const WGPUBindGroupEntry entries_1[] = {
-      {.binding = 0, .textureView = mask_view},
-      {.binding = 1, .sampler = mask_sampler_},
-  };
-
-  const WGPUBindGroupDescriptor bg_desc_1 = {
-      .layout = bgl_1,
-      .entryCount = 2,
-      .entries = entries_1,
-  };
-  bind_group_1_ = wgpuDeviceCreateBindGroup(ctx_.device, &bg_desc_1);
-  wgpuBindGroupLayoutRelease(bgl_1);
-}
-
-void RotatingCubeEffect::render(WGPURenderPassEncoder pass,
-                                const CommonPostProcessUniforms& u) {
-  rotation_ += 0.016f * 1.5f;
-
-  const vec3 camera_pos = vec3(0, 0, 5);
-  const vec3 target = vec3(0, 0, 0);
-  const vec3 up = vec3(0, 1, 0);
-
-  const mat4 view = mat4::look_at(camera_pos, target, up);
-  const float fov = 60.0f * 3.14159f / 180.0f;
-  const mat4 proj = mat4::perspective(fov, u.aspect_ratio, 0.1f, 100.0f);
-  const mat4 view_proj = proj * view;
-
-  const quat rot = quat::from_axis(vec3(0.3f, 1.0f, 0.2f), rotation_);
-  const mat4 T = mat4::translate(vec3(0, 0, 0));
-  const mat4 R = rot.to_mat();
-  const mat4 S = mat4::scale(vec3(1.5f, 1.5f, 1.5f));
-  const mat4 model = T * R * S;
-  const mat4 inv_model = model.inverse();
-
-  const Uniforms uniforms = {
-      .view_proj = view_proj,
-      .inv_view_proj = view_proj.inverse(),
-      .camera_pos_time = vec4(camera_pos.x, camera_pos.y, camera_pos.z, u.time),
-      .params = vec4(1.0f, 0.0f, 0.0f, 0.0f),
-      .resolution = u.resolution,
-  };
-
-  const ObjectData obj_data = {
-      .model = model,
-      .inv_model = inv_model,
-      .color = vec4(0.8f, 0.4f, 0.2f, 1.0f),
-      .params = vec4(1.0f, 0.0f, 0.0f, 0.0f),
-  };
-
-  wgpuQueueWriteBuffer(ctx_.queue, uniform_buffer_.buffer, 0, &uniforms,
-                       sizeof(Uniforms));
-  wgpuQueueWriteBuffer(ctx_.queue, object_buffer_.buffer, 0, &obj_data,
-                       sizeof(ObjectData));
-
-  wgpuRenderPassEncoderSetPipeline(pass, pipeline_);
-  wgpuRenderPassEncoderSetBindGroup(pass, 0, bind_group_0_, 0, nullptr);
-  wgpuRenderPassEncoderSetBindGroup(pass, 1, bind_group_1_, 0, nullptr);
-  wgpuRenderPassEncoderDraw(pass, 36, 1, 0, 0);
-}