CI: run exclusively GUI tests in the GUI test steps (#23933)

* CI: run exclusively GUI tests in the GUI test steps

* Fix linter error

Fix the unsupported operand type(s) for | (unsupported-binary-operation) linter error. It appears the linter uses or assumes Python <3.10.

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* CI: move __future__ import to the top of the module...

... to fix linter error.

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Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

.github/workflows/sub_buildUbuntu.yml

@@ -173,7 +173,8 @@ jobs:
         uses: ./.github/workflows/actions/runPythonTests
         with:
           testDescription: "GUI tests on build dir"
-          testCommand: xvfb-run ${{ env.builddir }}/bin/FreeCAD -t 0
+          # Use Python wrapper to run only GUI-registered tests with the built FreeCAD executable
+          testCommand: xvfb-run python3 ./.github/scripts/run_gui_tests.py "${{ env.builddir }}"
           logFile: ${{ env.logdir }}TestGUIBuild.log
           reportFile: ${{env.reportdir}}${{ env.reportfilename }}
 
@@ -207,7 +208,8 @@ jobs:
         uses: ./.github/workflows/actions/runPythonTests
         with:
           testDescription: "GUI tests on install"
-          testCommand: xvfb-run FreeCAD -t 0
+          # Use Python wrapper to run only GUI-registered tests using the installed FreeCAD
+          testCommand: xvfb-run python3 ./.github/scripts/run_gui_tests.py "FreeCAD"
           logFile: ${{ env.logdir }}TestGUIInstall.log
           reportFile: ${{env.reportdir}}${{ env.reportfilename }}