fix: explicit warnings on AMD ROCm arch/version fallbacks + Fast-Install arg order

setup.ps1:
- Fix Fast-Install argument order: packages before flags, consistent with
  all other Fast-Install calls in the file
  (was: Fast-Install --force-reinstall --index-url $url torch ...)
  (now: Fast-Install torch torchvision torchaudio --force-reinstall --index-url $url)
- Add explicit [WARN] substep when $HasROCm is true but arch mapping fails:
  - GPU arch detected but not in supported wheel list → names the arch and
    lists supported families so user knows exactly what to report
  - HIP SDK present (amd-smi path) but gcnArchName unreadable → instructs
    user to re-install the HIP SDK; previously fell back silently to CPU

install.sh:
- Add [WARN] to stderr before silent CPU fallback when AMD GPU is confirmed
  (rocminfo/amd-smi) but ROCm version cannot be read from any source
  (amd-smi, /opt/rocm/.info/version, hipconfig, dpkg, rpm)
- Add [WARN] to stderr when ROCm version is too old (< 6.0) with upgrade link

install.ps1 and setup.sh: no changes needed (already handle these paths correctly)

install.sh

@@ -1568,7 +1568,10 @@ get_torch_index_url() {
         if [ -n "$_rocm_tag" ]; then
             # Minimum supported: ROCm 6.0 (no PyTorch wheels exist for older)
             case "$_rocm_tag" in
-                rocm[1-5].*) echo "$_base/cpu"; return ;;
+                rocm[1-5].*)
+                    echo "[WARN] ROCm $_rocm_tag detected but PyTorch ROCm wheels require ROCm 6.0+ -- falling back to CPU-only PyTorch" >&2
+                    echo "[WARN] Upgrade ROCm: https://rocm.docs.amd.com/en/latest/deploy/linux/index.html" >&2
+                    echo "$_base/cpu"; return ;;
             esac
             # Supported tags; 6.5+ clips to rocm6.4, 7.3+ caps to rocm7.2.
             case "$_rocm_tag" in
@@ -1584,6 +1587,12 @@ get_torch_index_url() {
             esac
             return
         fi
+        # AMD GPU confirmed by rocminfo/amd-smi but ROCm version could not be
+        # read from any source (amd-smi, /opt/rocm/.info/version, hipconfig,
+        # dpkg, rpm).  Warn explicitly rather than silently installing CPU PyTorch.
+        echo "[WARN] AMD GPU detected but ROCm version could not be determined -- falling back to CPU-only PyTorch" >&2
+        echo "[WARN] Ensure one of the following is accessible: amd-smi, hipconfig, /opt/rocm/.info/version, rocm-core package" >&2
+        echo "[WARN] To install ROCm: https://rocm.docs.amd.com/en/latest/deploy/linux/index.html" >&2
         echo "$_base/cpu"; return
     fi
     # Parse CUDA version from nvidia-smi output (POSIX-safe, no grep -P)

studio/setup.ps1

@@ -1899,6 +1899,16 @@ if ($HasROCm -and $CuTag -eq "cpu") {
     $archFamily = if ($ROCmGfxArch -and $archFamilyMap.ContainsKey($ROCmGfxArch)) { $archFamilyMap[$ROCmGfxArch] } else { $null }
     if ($archFamily) {
         $ROCmIndexUrl = "$amdIndexBase/$archFamily/"
+    } elseif ($ROCmGfxArch) {
+        # GPU arch detected but not in the supported wheel map — warn explicitly
+        # so the user knows why they are getting CPU PyTorch instead of ROCm.
+        substep "[WARN] AMD GPU ($ROCmGfxArch) not in supported arch list -- falling back to CPU-only PyTorch" "Yellow"
+        substep "       Supported: gfx1200/1201 (RDNA 4), gfx1150/1151 (RDNA 3.5), gfx1100-1103 (RDNA 3), gfx90a, gfx908" "Yellow"
+    } else {
+        # HIP SDK present ($HasROCm=true via amd-smi) but gcnArchName was not
+        # readable — warn rather than silently falling back to CPU PyTorch.
+        substep "[WARN] AMD GPU detected (HIP SDK present) but GPU arch could not be read -- falling back to CPU-only PyTorch" "Yellow"
+        substep "       Arch detection requires hipinfo to report gcnArchName. Re-install the HIP SDK if this is unexpected." "Yellow"
     }
 }
 
@@ -1906,7 +1916,7 @@ $PyTorchWhlBase = if ($env:UNSLOTH_PYTORCH_MIRROR) { $env:UNSLOTH_PYTORCH_MIRROR
 
 if ($ROCmIndexUrl) {
     substep "installing PyTorch (AMD ROCm, $ROCmGfxArch)..."
-    $output = Fast-Install --force-reinstall --index-url $ROCmIndexUrl torch torchvision torchaudio | Out-String
+    $output = Fast-Install torch torchvision torchaudio --force-reinstall --index-url $ROCmIndexUrl | Out-String
     $torchInstallExit = $LASTEXITCODE
     if ($torchInstallExit -ne 0) {
         Write-Host "[WARN] AMD ROCm PyTorch install failed -- falling back to CPU" -ForegroundColor Yellow