Simplify CI workflow.

We don't need test-ubuntu-py-ver.yml since we can use "include".  Test
Python 3.14t as well.  More Python versions can be tested now we are
using setup-python.

.github/workflows/test-ubuntu-py-ver.yml

@@ -1,45 +0,0 @@
-# Test on Ubuntu with various Python versions
-name: Test Ubuntu, Python version compatiblity
-
-on:
-  workflow_dispatch:
-
-jobs:
-  build:
-    runs-on: ubuntu-latest
-
-    strategy:
-      fail-fast: false
-      matrix:
-        python-version: ['3.10', '3.11', '3.12', '3.13', '3.14', '3.14t']
-        cxx: [g++]
-        std: [c++11]
-        include:
-          # Add the appropriate docker image for each compiler.
-          # The images from teeks99/boost-python-test already have boost::python
-          # pre-reqs installed, see:
-          # https://github.com/teeks99/boost-python-test-docker
-          #- cxx: clang++
-          #  docker-img: teeks99/boost-python-test:clang-21_1.89.0
-          - cxx: g++
-            docker-img: teeks99/boost-python-test:gcc-15_1.89.0
-
-    container:
-      image: ${{ matrix.docker-img }}
-
-    steps:
-    - uses: actions/checkout@v5
-    - name: setup python
-      uses: actions/setup-python@v5
-      with:
-        python-version: ${{ matrix.python-version }}
-    - name: setup prerequisites
-      run: |
-        echo "CXX=${{ matrix.cxx }}" >> "$GITHUB_ENV"
-        echo "CXX_STD=${{ matrix.std }}" >> "$GITHUB_ENV"
-    - name: build
-      run: |
-        .github/run-faber.sh
-    - name: test
-      run: |
-        .github/run-faber.sh test.report

.github/workflows/test-ubuntu.yml

@@ -17,17 +17,19 @@ jobs:
         cxx: [g++, clang++]
         std: [c++11, c++14, c++17]
         include:
-          # Add the appropriate docker image for each compiler.
-          # The images from teeks99/boost-python-test already have boost::python
-          # pre-reqs installed, see:
-          # https://github.com/teeks99/boost-python-test-docker
-          - cxx: clang++
-            docker-img: teeks99/boost-python-test:clang-21_1.89.0
-          - cxx: g++
-            docker-img: teeks99/boost-python-test:gcc-15_1.89.0
+          # Also test with free-threaded build of Python
+          - python-version: '3.14t'
+            cxx: clang+
+            std: c++17
 
     container:
-      image: ${{ matrix.docker-img }}
+      # Add the appropriate docker image for the compiler.
+      # The images from teeks99/boost-python-test already have boost::python
+      # pre-reqs installed, see:
+      # https://github.com/teeks99/boost-python-test-docker
+      image: ${{ matrix.cxx == 'g++' &&
+        'teeks99/boost-python-test:gcc-15_1.89.0' ||
+        'teeks99/boost-python-test:clang-21_1.89.0' }}
 
     steps:
     - uses: actions/checkout@v5