fix(cnn_v3): shadow pass — 5 bugs fixed, labels in gbuf_viewHEADmain

1. Camera Y-inversion: proj.m[5] = -proj.m[5] in upload_scene_data
   + WGPUFrontFace_CCW on raster pipeline.
2. Shadow formula: replace shadowWithStoredDistance with 64-step
   IQ soft shadow (8*d/t, unbounded).
3. Local→world SDF scale: d *= length(obj.model[0].xyz).
4. Shadow bias: use rasterized normal from normal_mat_tex (binding 4)
   instead of light direction — fixes terminator self-shadow on spheres.
5. ShaderComposer: GBufViewEffect now resolves #include via
   ShaderComposer::Get().Compose().

Also: per-tile channel labels in gbuf_view.wgsl via debug_str.
Scene simplified to 1 cube + 1 sphere for debugging (restore TODO).
Scale propagation for pulsating sphere confirmed correct end-to-end.

handoff(Gemini): shadow validated. Next: restore full scene in
GBufferEffect::set_scene() (20 cubes + 4 spheres, 2 lights), then
run training pass per cnn_v3/docs/HOWTO.md §3.

1 files changed, 4 insertions, 3 deletions

diff --git a/TODO.md b/TODO.md
index e855384..f97ef0e 100644
--- a/TODO.md
+++ b/TODO.md
@@ -64,11 +64,12 @@ Ongoing shader code hygiene for granular, reusable snippets.
 
 **Design:** `cnn_v3/docs/CNN_V3.md` | All phases 1–7 complete. Runtime pipeline operational.
 
-**Current pipeline:** `GBufferEffect` → `GBufDeferredEffect` → sink (debug view: albedo×diffuse)
+**Current pipeline:** `GBufferEffect` → `GBufDeferredEffect` → `GBufViewEffect` → sink
+
+**Shadow pass status:** ✅ Fixed and re-enabled. Cube + sphere shadows correct. Pulsating sphere scale confirmed correct end-to-end. Scene is currently simplified (1 cube + 1 sphere, 1 light) for debugging.
 
 **Active work:**
-- [ ] Fix/validate shadow pass (`gbuf_shadow.wgsl`) — currently disabled in deferred
-- [ ] Re-enable shadow in `GBufDeferredEffect` once validated
+- [ ] Restore full scene in `GBufferEffect::set_scene()` (20 cubes + 4 spheres, 2 lights)
 - [ ] Run first real training pass — see `cnn_v3/docs/HOWTO.md` §3
 
 **Pending (lower priority):**