build(autoconf): add support for Python 3.14

[AlessandroPomponio]

🐛 Issue

ado-autoconf currently depends on fastai, which in turn depends on spacy. While spaCy v3.8.14 provides Python 3.14 wheels on its GitHub release page, these wheels are not yet published on PyPI.

This prevents standard installations from resolving dependencies when using Python 3.14, since package managers (e.g., pip) rely on PyPI.

• Upstream tracking: Missing cp314 wheels for v3.8.14 on PyPI explosion/spaCy#13949
• Related context: build: add support for Python 3.14 #966

💥 Impact

• ado-autoconf cannot reliably support Python 3.14 via standard dependency resolution
• Users attempting to install with Python 3.14 may encounter installation failures
• Workarounds (e.g., manually installing wheels from GitHub) are not suitable for most users

✅ Current status

• Python 3.14 support is effectively blocked by upstream packaging gaps
• Waiting on spacy to publish wheels to PyPI

🔧 Proposed action

Once spaCy publishes Python 3.14 wheels to PyPI:

1. Validate ado-autoconf installation on Python 3.14 using standard pip workflows
2. Verify end-to-end installation and runtime behavior

✅ Done when

• spaCy publishes Python 3.14 wheels on PyPI
• ado-autoconf installs successfully on Python 3.14 via PyPI only
• CI tests for autoconf with Python 3.14 are re-enabled
• Python 3.14 support is verified and documented in ado-autoconf