feat(sequence): port Scene1Effect + fix seq_compiler absolute time bug

- Add Scene1 effect: raymarching cube+sphere+ground (reflections, shadows)
- Fix scene1.wgsl: binding 0→2, CommonUniforms→UniformsSequenceParams
- Replace Heptagon+Placeholder stub in heptagon_scene with Scene1
- Fix seq_compiler.py: emit seq.start_time+effect.start/end (absolute times)
  so dispatch_render active check works correctly for all sequences

Bug: effects in sequences starting after t=0 were never active because
local times (e.g. 0-8) never satisfied params.time<end for absolute time 20+.

34/34 tests passing.

handoff(Gemini): seq_compiler now emits absolute effect times. All existing
sequences affected — verify visual output across the full timeline.

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

1 files changed, 1 insertions, 1 deletions

diff --git a/tools/seq_compiler.py b/tools/seq_compiler.py
index 18d5a1f..2e51574 100755
--- a/tools/seq_compiler.py
+++ b/tools/seq_compiler.py
@@ -437,7 +437,7 @@ class {class_name} : public Sequence {{
       .effect = std::make_shared<{effect.class_name}>(ctx,
                 std::vector<std::string>{{{inputs_str}}},
                 std::vector<std::string>{{{outputs_str}}},
-                {effect.start}f, {effect.end}f),
+                {seq.start_time + effect.start}f, {seq.start_time + effect.end}f),
       .input_nodes = {{{inputs_str}}},
       .output_nodes = {{{outputs_str}}},
       .execution_order = {effect.execution_order}