ci: test Python 3.11-3.14 and require Python 3.11 (#356)

Python 3.10 reaches end of life in October 2026 and no PromptManager
users run it; 3.14 is current and was untested. The test matrix runs
3.11-3.14 on Linux, Windows and macOS, bandit runs on 3.11, and
requires-python is >=3.11 so the package no longer claims a version CI
does not test. The packaging test drops its 3.10-only tomllib fallback.
The required checks follow the matrix (py3.10 -> py3.14).

.github/workflows/code-quality.yml

@@ -26,10 +26,10 @@ jobs:
     steps:
       - uses: actions/checkout@v7
 
-      - name: Set up Python 3.10
+      - name: Set up Python 3.11
         uses: actions/setup-python@v7
         with:
-          python-version: "3.10"
+          python-version: "3.11"
 
       - name: Install bandit
         run: pip install bandit[toml]