Studio: exclude mlx-lm 0.31.3 (broke gemma4/qwen3_5 QK-norm load on Apple Silicon) (#6803)

* Studio: exclude mlx-lm 0.31.3 (broke gemma4/qwen3_5 QK-norm load)

mlx-lm 0.31.3 regressed the QK-norm archs: its strict load_weights rejects the
q_norm/k_norm tensors with "Received N parameters not in model", so gemma4 and
qwen3_5 checkpoints fail to load. Studio installs the MLX stack unpinned at
latest, which pulls 0.31.3. Verified on a real macos-14 runner: gemma4 fails to
load on 0.31.3 but loads and generates coherently on 0.31.2 and on git-main
(future 0.31.4). See mlx-lm #1242.

Exclude just that release (!=0.31.3) in the installer and the self-heal floor so
--upgrade still resolves to the newest good build, and treat an already-installed
0.31.3 as unsatisfied so the self-heal replaces it.

* Studio MLX: cover fresh-install path + robust bad-version compare

Address PR review:
- Fresh install.sh (Apple Silicon) runs the base 'uv pip install unsloth' with
  SKIP_STUDIO_BASE=1, skipping the guarded MLX-stack step, so transitive
  resolution could still pull mlx-lm 0.31.3. install.sh already exports
  UV_OVERRIDE -> overrides-darwin-arm64.txt before that install, so exclude
  mlx-lm 0.31.3 there too; this also strengthens the self-heal (same override).
- Match the known-bad version with parsed packaging.Version so 0.31.3 == 0.31.3.0
  (trailing-zero normalization) instead of raw string equality.

* Studio: exclude mlx-lm 0.31.3 on the fresh Apple Silicon install too

The overrides file only applies via UV_OVERRIDE when it exists relative to the
script, which is not true for a curl-piped install, and the guarded MLX step in
install_python_stack.py is skipped there (SKIP_STUDIO_BASE=1). So the base
install could still resolve the transitive mlx-lm to the broken 0.31.3. Append
mlx-lm!=0.31.3 to the base install on Apple Silicon (empty elsewhere), so the
fresh path pins away from 0.31.3 without waiting for the runtime self-heal.

* Studio: exclude mlx-lm 0.31.3 on the migrated install; keep the >=0.22.0 floor

The with-deps migrated install did not append ${_MLX_LM_EXCLUDE_ARG:-}, so a
curl-piped Apple Silicon migration (no repo overrides file, UV_OVERRIDE unset)
could resolve mlx-lm 0.31.3 transitively. Append the exclusion there, matching
the fresh install path. The no-torch migration is left alone since --no-deps
never resolves mlx-lm (same as the fresh no-torch path).

Also restore the >=0.22.0 floor in overrides-darwin-arm64.txt: a uv override
replaces the transitive constraint, so a bare !=0.31.3 could let the resolver
drop below the supported minimum that mlx_repair.py enforces at runtime.

* Triage huggingface_hub 1.22.0 / fastapi / multiprocess scanner false positives

The scan-packages gate red-failed on all three shards after transitive deps
bumped. Every new CRITICAL is a benign false positive, verified against upstream:

- huggingface_hub 1.22.0 added _sandbox.py for the remote HF sandbox feature.
  Its job-startup bootstrap string (fetch sbx-server into the container /tmp and
  exec it) and the SandboxPool host-reservation loop trip the staged-dropper and
  C2-loop heuristics; that script runs inside a remote HF container, not on the
  user machine. The bump also re-hashed the already-reviewed benign polling loops
  in hf_api.py and utils/_http.py. The PyPI artifact is byte-identical to the
  official v1.22.0 tag.
- fastapi 0.139.0 routing.py re-hashed the websocket keepalive while-True loop;
  byte-identical to upstream 0.139.0.
- multiprocess 0.70.19 forkserver.py and tests/__init__.py re-hashed the AF_UNIX
  fork-server IPC and fd-inheritance tests; genuine uqfoundation release, local
  IPC not network.

Added 7 reviewed allowlist entries (no blind regenerate). All three shards
(hf-stack, studio, extras) exit 0 locally.

* Tighten mlx-lm 0.31.3 exclusion comments

* Trim mlx-lm 0.31.3 exclusion comments

install.sh

@@ -1442,8 +1442,14 @@ if [ "$_NO_TORCH_FLAG" = true ] || [ "$MAC_INTEL" = true ]; then
     SKIP_TORCH=true
 fi
 
+# Apple Silicon: exclude broken mlx-lm 0.31.3 (QK-norm load regression for
+# gemma4 / qwen3_5; mlx-lm #1242). A curl-piped install has no overrides file
+# and skips the guarded MLX step (SKIP_STUDIO_BASE=1), so this is the only cover.
+_MLX_LM_EXCLUDE_ARG=""
+
 # Apple Silicon: override mlx-vlm / mlx-lm's transformers pin (see overrides file).
 if [ "$OS" = "macos" ] && [ "$_ARCH" = "arm64" ]; then
+    _MLX_LM_EXCLUDE_ARG="mlx-lm!=0.31.3"
     _OVERRIDES_FILE="$(cd "$(dirname "$0" 2>/dev/null || echo ".")" && pwd)/studio/backend/requirements/single-env/overrides-darwin-arm64.txt"
     if [ -f "$_OVERRIDES_FILE" ]; then
         # uv splits UV_OVERRIDE on whitespace, so a repo path with whitespace
@@ -2679,9 +2685,11 @@ if [ "$_MIGRATED" = true ]; then
             run_install_cmd_retry "install no-torch runtime deps" uv pip install --python "$_VENV_PY" --no-deps -r "$_NO_TORCH_RT"
         fi
     else
+        # Pin mlx-lm away from 0.31.3 here too: a curl-piped migration has no
+        # overrides file, so UV_OVERRIDE is unset and this positional is the only cover.
         run_install_cmd_retry "install unsloth (migrated)" uv pip install --python "$_VENV_PY" \
             --reinstall-package unsloth --reinstall-package unsloth-zoo \
-            "unsloth>=2026.6.9" "unsloth-zoo>=2026.6.7"
+            "unsloth>=2026.6.9" "unsloth-zoo>=2026.6.7" ${_MLX_LM_EXCLUDE_ARG:-}
     fi
     if [ "$STUDIO_LOCAL_INSTALL" = true ]; then
         substep "overlaying local repo (editable)..."
@@ -2912,7 +2920,7 @@ elif [ -n "$TORCH_INDEX_URL" ]; then
             "unsloth-zoo @ git+https://github.com/unslothai/unsloth-zoo"
     else
         run_install_cmd_retry "install unsloth" uv pip install --python "$_VENV_PY" \
-            --upgrade-package unsloth -- "$PACKAGE_NAME"
+            --upgrade-package unsloth -- "$PACKAGE_NAME" ${_MLX_LM_EXCLUDE_ARG:-}
     fi
     # AMD ROCm: repair torch if the unsloth/unsloth-zoo install pulled in
     # CUDA torch from PyPI, overwriting the ROCm wheels installed in Step 1.