fix(rebase): adapt to dev's split tensor_upload/_g API + fault-injection hook

Dev split coli_cuda_tensor_upload into two symbols: the plain 7-arg
tensor_upload (no gs) for fmt!=4, and tensor_upload_g (8-arg, with gs)
for fmt=4 grouped. The DLL-side _g sets a g_upload_gs global the plain
upload reads internally. Adapted all call sites:

- colibri.c: qt_cuda_upload already dispatches (_g for fmt=4, plain
  otherwise) — kept dev's version. layer_cuda_shard_kvb was calling the
  plain upload with gs; switched to tensor_upload_g.
- backend_loader.c: the C-API wrapper matches dev's 7-arg signature;
  tensor_upload_g dispatched separately.
- backend_cuda.cu: cache-hit check uses g_upload_gs (not a gs param);
  coli_cuda_matmul dispatches _g when gs>0; the grouped-expert host
  fallback quant_matmul calls pass gs=0,ng=1 (host tier is per-row).
- Kept dev's fault-injection hook, scale_count field, and fmt=4 support
  in the grouped-expert path (all_q4/any_g4 tracking).
- tests: kept dev's comprehensive tensor_upload test (cached reuse,
  temp-buffer survival, upload-failure accounting, fault injection).

Build-verified: colibri.exe + coli_cuda.dll both compile clean.

c/backend_loader.c

@@ -325,9 +325,9 @@ int coli_cuda_attention_absorb(ColiCudaTensor *kv_b, float *ctx, const float *q,
 }
 
 int coli_cuda_tensor_upload(ColiCudaTensor **tensor, const void *weights,
-                            const float *scales, int fmt, int I, int O, int device, int gs){
+                            const float *scales, int fmt, int I, int O, int device){
     if(!g_cuda.available) return 0;
-    return g_cuda.tensor_upload(tensor, weights, scales, fmt, I, O, device, gs);
+    return g_cuda.tensor_upload(tensor, weights, scales, fmt, I, O, device);
 }
 
 int coli_cuda_tensor_upload_g(ColiCudaTensor **tensor, const void *weights, const float *scales, int fmt, int I, int O, int device, int gs){