Use envsitepackagesdir in coverage path

Update tox.ini to set pytest --cov to {envsitepackagesdir}/dlclivegui instead of the project module name. This ensures coverage collects from the package installed into the tox environment (matching the GitHub Actions job) and avoids missing coverage when the package is not imported from the project root.

Author: C-Achard

tox.ini

@@ -24,7 +24,7 @@ setenv =
 # Keep behavior aligned with your GitHub Actions job:
 commands =
     pytest -m "not hardware" --maxfail=1 --disable-warnings \
-        --cov=dlclivegui \
+        --cov={envsitepackagesdir}/dlclivegui \
         --cov-report=xml:{toxinidir}/.coverage.{envname}.xml \
         --cov-report=term-missing \
         {posargs}