ci : use hf-jobs-cpu-performance, disable pytest workers (#29369)

* ci : disable pytest workers in server sanitize workflow

Assisted-by: pi:llama.cpp/Qwen3.8-27B

* cont : switch to `cpu-performance`

* Revert "ci : disable pytest workers in server sanitize workflow"

This reverts commit 76ece3b7cf.

* cont : use 2 pytest workers

* cont : try automatic pytest workers

* cont : use 4 pytest workers

.github/workflows/server-sanitize.yml

@@ -45,7 +45,7 @@ concurrency:
 
 jobs:
   server:
-    runs-on: hf-jobs-cpu-xl
+    runs-on: hf-jobs-cpu-performance
 
     strategy:
       matrix:
@@ -116,7 +116,7 @@ jobs:
         run: |
           source .venv/bin/activate
           cd tools/server/tests
-          PYTEST_WORKERS=1 ./tests.sh
+          PYTEST_WORKERS=4 ./tests.sh
 
       - name: Slow tests
         id: server_integration_tests_slow
@@ -124,4 +124,4 @@ jobs:
         run: |
           source .venv/bin/activate
           cd tools/server/tests
-          PYTEST_WORKERS=1 SLOW_TESTS=1 ./tests.sh
+          PYTEST_WORKERS=4 SLOW_TESTS=1 ./tests.sh