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, 31 insertions, 1 deletions

diff --git a/cnn_v3/shaders/gbuf_view.wgsl b/cnn_v3/shaders/gbuf_view.wgsl
index a5e6c91..3e7d1ff 100644
--- a/cnn_v3/shaders/gbuf_view.wgsl
+++ b/cnn_v3/shaders/gbuf_view.wgsl
@@ -9,6 +9,8 @@
 //   Row 3: ch12(m1.r)  ch13(m1.g)  ch14(m1.b)  ch15(m2.r)
 //   Row 4: ch16(m2.g)  ch17(m2.b)  ch18(shdw)  ch19(trns)
 
+#include "debug/debug_print"
+
 struct GBufViewUniforms { resolution: vec2f }
 
 @group(0) @binding(0) var feat0:   texture_2d<u32>;
@@ -93,5 +95,33 @@ fn fs_main(@builtin(position) pos: vec4f) -> @location(0) vec4f {
         disp = clamp(v, 0.0, 1.0);
     }
 
-    return vec4f(disp, disp, disp, 1.0);
+    var out = vec4f(disp, disp, disp, 1.0);
+
+    // Label at top-left of each tile
+    let tile_w = u.resolution.x / 4.0;
+    let tile_h = u.resolution.y / 5.0;
+    let origin = vec2f(f32(col) * tile_w + 4.0, f32(row) * tile_h + 4.0);
+    switch ch {
+        case  0u: { out = debug_str(out, pos.xy, origin, vec4u(0x616C622Eu, 0x72000000u, 0u, 0u), 5u); } // alb.r
+        case  1u: { out = debug_str(out, pos.xy, origin, vec4u(0x616C622Eu, 0x67000000u, 0u, 0u), 5u); } // alb.g
+        case  2u: { out = debug_str(out, pos.xy, origin, vec4u(0x616C622Eu, 0x62000000u, 0u, 0u), 5u); } // alb.b
+        case  3u: { out = debug_str(out, pos.xy, origin, vec4u(0x6E726D2Eu, 0x78000000u, 0u, 0u), 5u); } // nrm.x
+        case  4u: { out = debug_str(out, pos.xy, origin, vec4u(0x6E726D2Eu, 0x79000000u, 0u, 0u), 5u); } // nrm.y
+        case  5u: { out = debug_str(out, pos.xy, origin, vec4u(0x64657074u, 0x68000000u, 0u, 0u), 5u); } // depth
+        case  6u: { out = debug_str(out, pos.xy, origin, vec4u(0x647A6478u, 0u, 0u, 0u), 4u); }          // dzdx
+        case  7u: { out = debug_str(out, pos.xy, origin, vec4u(0x647A6479u, 0u, 0u, 0u), 4u); }          // dzdy
+        case  8u: { out = debug_str(out, pos.xy, origin, vec4u(0x6D617469u, 0x64000000u, 0u, 0u), 5u); } // matid
+        case  9u: { out = debug_str(out, pos.xy, origin, vec4u(0x7072762Eu, 0x72000000u, 0u, 0u), 5u); } // prv.r
+        case 10u: { out = debug_str(out, pos.xy, origin, vec4u(0x7072762Eu, 0x67000000u, 0u, 0u), 5u); } // prv.g
+        case 11u: { out = debug_str(out, pos.xy, origin, vec4u(0x7072762Eu, 0x62000000u, 0u, 0u), 5u); } // prv.b
+        case 12u: { out = debug_str(out, pos.xy, origin, vec4u(0x6D312E72u, 0u, 0u, 0u), 4u); }          // m1.r
+        case 13u: { out = debug_str(out, pos.xy, origin, vec4u(0x6D312E67u, 0u, 0u, 0u), 4u); }          // m1.g
+        case 14u: { out = debug_str(out, pos.xy, origin, vec4u(0x6D312E62u, 0u, 0u, 0u), 4u); }          // m1.b
+        case 15u: { out = debug_str(out, pos.xy, origin, vec4u(0x6D322E72u, 0u, 0u, 0u), 4u); }          // m2.r
+        case 16u: { out = debug_str(out, pos.xy, origin, vec4u(0x6D322E67u, 0u, 0u, 0u), 4u); }          // m2.g
+        case 17u: { out = debug_str(out, pos.xy, origin, vec4u(0x6D322E62u, 0u, 0u, 0u), 4u); }          // m2.b
+        case 18u: { out = debug_str(out, pos.xy, origin, vec4u(0x73686477u, 0u, 0u, 0u), 4u); }          // shdw
+        default:  { out = debug_str(out, pos.xy, origin, vec4u(0x74726E73u, 0u, 0u, 0u), 4u); }          // trns
+    }
+    return out;
 }