ci: pin to Python 3.8 (ST4 runtime) with explicit comment about ST3 vs ST4 Python versions

Agent-Logs-Url: https://github.com/asfaltboy/SublimeTestPlier/sessions/648a7aeb-d19a-4574-bafd-c07b83df5695

Co-authored-by: asfaltboy <321520+asfaltboy@users.noreply.github.com>

Author: Copilot

.github/workflows/ci.yml

@@ -11,7 +11,11 @@ jobs:
       - uses: actions/checkout@v4
       - uses: actions/setup-python@v5
         with:
-          python-version: '3.11'
+          # Sublime Text 3 embeds Python 3.3; ST4 embeds Python 3.8.
+          # Python 3.3 is EOL and unavailable on GitHub Actions runners,
+          # so we test against 3.8 (the ST4 runtime) as the minimum
+          # supported version available on CI.
+          python-version: '3.8'
       - name: Install dependencies
         run: |
           python -m pip install --upgrade pip