Point the llama assert at the right root, and name the Intel limitation

The tauri leg installs to the legacy root because --tauri refuses a custom
UNSLOTH_STUDIO_HOME. Its install succeeds end to end, but llama.cpp lives at
<root>/llama.cpp while the venv is at <root>/studio, so the assert was pointed one
level too deep.

On macos-15-intel /usr/bin/git keeps working once the CLT are gone, so it is not
CLT-provided there and no masking can remove it, while cc and clang do become
stubs. Calling that 'masking failed' was wrong. That leg allowlists git
explicitly and says why, so the assert stays strict everywhere else.

.github/workflows/clean-machine-install-ci.yml

@@ -83,8 +83,9 @@ jobs:
           # OS-version dimension.
           - {os: macos-15, mode: mask,  delivery: pipe,  flags: '',           experimental: false}
           - {os: macos-26, mode: mask,  delivery: file,  flags: '',           experimental: true}
-          # Intel pins python 3.12, not 3.13 -- informational only.
-          - {os: macos-15-intel, mode: mask, delivery: file, flags: '',       experimental: true}
+          # Intel pins python 3.12 and its /usr/bin/git is not CLT-provided, so it
+          # survives masking. Informational only.
+          - {os: macos-15-intel, mode: mask, delivery: file, flags: '',       experimental: true, allow_working: 'git'}
 
     steps:
       # checkout FIRST: it needs a working git, which masking then takes away.
@@ -118,7 +119,8 @@ jobs:
         if: matrix.mode == 'mask'
         run: |
           set -a; . ./clean-machine.env; set +a
-          bash .github/scripts/clean-machine-assert.sh absent
+          UNSLOTH_CLEAN_ALLOW_WORKING='${{ matrix.allow_working }}' \
+            bash .github/scripts/clean-machine-assert.sh absent
 
       - name: Install
         id: install
@@ -189,9 +191,10 @@ jobs:
         run: |
           set -a; . ./clean-machine.env; set +a
           # The tauri leg cannot honour UNSLOTH_STUDIO_HOME (see the Install step), so
-          # it installed into the legacy root and that is where to look.
+          # it installed into the legacy root. llama.cpp sits at <root>/llama.cpp and
+          # the venv at <root>/studio, so this is ~/.unsloth, not ~/.unsloth/studio.
           if [ "${{ matrix.delivery }}" = "tauri" ]; then
-            HOME_DIR="$HOME/.unsloth/studio"
+            HOME_DIR="$HOME/.unsloth"
           else
             HOME_DIR="$UNSLOTH_STUDIO_HOME"
           fi