tox.ini: skip install for dlclive-github env

Update dlclive-github testenv to run compatibility tests against GitHub main without installing the local package. Adds a comment explaining the rationale, sets package = skip, adds pytest to deps, and inserts a small diagnostic python command to print the imported dlclive file and deeplabcut-live version before running the compatibility test.

Author: C-Achard

tox.ini

@@ -63,13 +63,18 @@ commands =
     pytest -m dlclive_compat tests/compat/test_dlclive_package_compat.py -q
 
 # Run locally : tox -e dlclive-github
+# These do not need live-GUI so to make sure it is the main version that is tested,
+# we skip installing the package (and its DLCLive requirement)
 [testenv:dlclive-github]
 description = DLCLive compatibility tests against GitHub main
+package = skip
 passenv =
     {[testenv:dlclive]passenv}
 deps =
+    pytest
     git+https://github.com/DeepLabCut/DeepLabCut-live.git@main
 commands =
+    python -c "import dlclive, importlib.metadata; print('dlclive:', dlclive.__file__); print('version:', importlib.metadata.version('deeplabcut-live'))"
     pytest -m dlclive_compat tests/compat/test_dlclive_package_compat.py -q
 
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