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, 49 deletions

diff --git a/src/effects/particle_spray_effect.cc b/src/effects/particle_spray_effect.cc
deleted file mode 100644
index 1acf67d..0000000
--- a/src/effects/particle_spray_effect.cc
+++ /dev/null
@@ -1,49 +0,0 @@
-// This file is part of the 64k demo project.
-// It implements the ParticleSprayEffect.
-
-#include "effects/particle_spray_effect.h"
-#include "gpu/gpu.h"
-#include "gpu/post_process_helper.h"
-#include "gpu/shaders.h"
-#include <vector>
-
-// --- ParticleSprayEffect ---
-ParticleSprayEffect::ParticleSprayEffect(const GpuContext& ctx) : Effect(ctx) {
-  std::vector<Particle> init_p(NUM_PARTICLES);
-  for (Particle& p : init_p)
-    p.pos[3] = 0.0f;
-  particles_buffer_ = gpu_create_buffer(
-      ctx_.device, sizeof(Particle) * NUM_PARTICLES,
-      WGPUBufferUsage_Storage | WGPUBufferUsage_Vertex, init_p.data());
-  ResourceBinding cb[] = {{particles_buffer_, WGPUBufferBindingType_Storage},
-                          {uniforms_.get(), WGPUBufferBindingType_Uniform}};
-  compute_pass_ =
-      gpu_create_compute_pass(ctx_.device, particle_spray_compute_wgsl, cb, 2);
-  compute_pass_.workgroup_size_x = (NUM_PARTICLES + 63) / 64;
-  ResourceBinding rb[] = {
-      {particles_buffer_, WGPUBufferBindingType_ReadOnlyStorage},
-      {uniforms_.get(), WGPUBufferBindingType_Uniform}};
-  render_pass_ = gpu_create_render_pass(ctx_.device, ctx_.format,
-                                        particle_render_wgsl, rb, 2);
-  render_pass_.vertex_count = 6;
-  render_pass_.instance_count = NUM_PARTICLES;
-}
-void ParticleSprayEffect::compute(WGPUCommandEncoder e,
-                                  const CommonPostProcessUniforms& uniforms) {
-  uniforms_.update(ctx_.queue, uniforms);
-  WGPUComputePassEncoder pass = wgpuCommandEncoderBeginComputePass(e, nullptr);
-  wgpuComputePassEncoderSetPipeline(pass, compute_pass_.pipeline);
-  wgpuComputePassEncoderSetBindGroup(pass, 0, compute_pass_.bind_group, 0,
-                                     nullptr);
-  wgpuComputePassEncoderDispatchWorkgroups(pass, compute_pass_.workgroup_size_x,
-                                           1, 1);
-  wgpuComputePassEncoderEnd(pass);
-}
-void ParticleSprayEffect::render(WGPURenderPassEncoder pass,
-                                 const CommonPostProcessUniforms& uniforms) {
-  (void)uniforms;
-  wgpuRenderPassEncoderSetPipeline(pass, render_pass_.pipeline);
-  wgpuRenderPassEncoderSetBindGroup(pass, 0, render_pass_.bind_group, 0,
-                                    nullptr);
-  wgpuRenderPassEncoderDraw(pass, 6, NUM_PARTICLES, 0, 0);
-}