fix(studio): source-build fallback prefers Unsloth's tested tag over upstream latest (#4593)

* fix(studio): source-build fallback prefers Unsloth's tested tag over upstream latest

When the prebuilt install fails and falls back to source build,
--resolve-llama-tag now queries the Unsloth release repo
(unslothai/llama.cpp) first to get the latest tested/approved tag
(e.g. b8508), instead of going straight to ggml-org/llama.cpp which
may return a newer untested tag (e.g. b8514).

This ensures the source-build fallback compiles the same version that
the prebuilt path would have installed, rather than a potentially
incompatible bleeding-edge release.

Resolution order for "latest":
  1. Unsloth release repo (tested/approved)
  2. ggml-org upstream (bleeding-edge)
  3. Raw requested tag string (last resort)

Changes:
- resolve_requested_llama_tag() accepts optional published_repo param
  with docstring explaining the resolution order
- CLI --resolve-llama-tag passes --published-repo through
- setup.sh and setup.ps1 pass --published-repo to --resolve-llama-tag
  with inline comments explaining the preference

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

studio/setup.ps1

@@ -1314,7 +1314,10 @@ if ($resolveExit -ne 0 -or [string]::IsNullOrWhiteSpace($ResolvedLlamaTag)) {
     if ($resolveOutput) {
         $resolveOutput | ForEach-Object { Write-Host $_ }
     }
-    $fallbackOutput = & python "$PSScriptRoot\install_llama_prebuilt.py" --resolve-llama-tag $RequestedLlamaTag 2>$null
+    # Resolve the llama.cpp tag for source-build fallback. Pass --published-repo
+    # so the resolver prefers Unsloth's tested tag (e.g. b8508) over the upstream
+    # bleeding-edge tag (e.g. b8514) from ggml-org/llama.cpp.
+    $fallbackOutput = & python "$PSScriptRoot\install_llama_prebuilt.py" --resolve-llama-tag $RequestedLlamaTag --published-repo $HelperReleaseRepo 2>$null
     $fallbackExit = $LASTEXITCODE
     $ResolvedLlamaTag = if ($fallbackExit -eq 0 -and $fallbackOutput) {
         ($fallbackOutput | Select-Object -Last 1).ToString().Trim()