The PyYAML floor does not install on Python 3.14 #126

The yaml extra declares PyYAML>=6, which resolves to 6.0 at the bottom of the range. 6.0 ships no cp314 wheel, so on Python 3.14 the resolver falls through to the sdist and the build fails:

Failed to build `pyyaml==6.0`

3.10 is fine; 3.14 is not. The declared floor is unsatisfiable on the newest supported interpreter.

Nothing reports it: every gate resolves highest, so the bottom of the range is never exercised.

Reproduce

uv venv --python 3.14 .venv-lowest
VIRTUAL_ENV=.venv-lowest uv pip install --resolution lowest-direct ".[yaml]"

Fix

A marked floor keeps 6.0 usable where it works rather than raising it for everyone:

"PyYAML>=6; python_version < '3.14'",
"PyYAML>=X; python_version >= '3.14'",

Find X by installing candidate versions on 3.14 rather than guessing.

Found by a lower-bound audit across the org, prompted by modern-python/.github#107. That issue proposes a CI job that would catch this class of defect standing; right now every gate resolves highest, so no floor is ever exercised.

13 of 23 repos audited had at least one broken floor. faststream-outbox had six and is now green at the lower bound on every supported interpreter.