chore: add Python 3.14 to CI matrix and pyproject classifiers

Python 3.14 went GA in October 2025. With the modernization phases 1-5
landed (pathlib support, UTC datetimes, collections.abc imports,
Font.color non-mutation, uv-managed deps, pyright strict on public API),
the codebase already runs clean on 3.14 locally — adding it to the CI
matrix is the last missing surface.

Changes:
- .github/workflows/ci.yml: append "3.14" to the test job matrix
- pyproject.toml: add 'Programming Language :: Python :: 3.14' classifier

requires-python stays at >=3.9; no lower-version drop.

Verification (local, CPython 3.14.4):
- python3 -m pytest tests/ -q     → 3485 passed in 6.56s
- python3 -m ruff check src tests → All checks passed
- python3 -m ruff format --check  → 215 files already formatted
- python3 -m behave features/     → 1048 scenarios, 0 failed; 3151 steps, 0 failed

Refs #29.

Author: MHoroszowski

.github/workflows/ci.yml

@@ -65,7 +65,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        python-version: ["3.9", "3.10", "3.11", "3.12", "3.13"]
+        python-version: ["3.9", "3.10", "3.11", "3.12", "3.13", "3.14"]
     steps:
       - uses: actions/checkout@v4
       - name: Install uv

pyproject.toml

@@ -19,6 +19,7 @@ classifiers = [
     "Programming Language :: Python :: 3.11",
     "Programming Language :: Python :: 3.12",
     "Programming Language :: Python :: 3.13",
+    "Programming Language :: Python :: 3.14",
     "Topic :: Office/Business :: Office Suites",
     "Topic :: Software Development :: Libraries",
 ]