chore: bump uv to 0.13.4 in every pin

Dependabot moved uv in pyproject.toml alone, while validate.yml and
CONTRIBUTING kept 0.12.9. Both pins move together, and a test now
fails when a package pinned in both carries two versions.

.github/workflows/validate.yml

@@ -247,7 +247,7 @@ jobs:
       # setuptools reads pyproject.toml for the packaging guard, and uv builds
       # the PyPI package the way a release builds it.
       - name: Install dependencies
-        run: pip install pyyaml "jsonschema[format-nongpl]==4.26.0" "markdown==3.10.2" "pyte==0.8.2" "hypothesis==6.170.8" "vermin==1.9.2" "setuptools==80.9.0" "uv==0.12.9"
+        run: pip install pyyaml "jsonschema[format-nongpl]==4.26.0" "markdown==3.10.2" "pyte==0.8.2" "hypothesis==6.170.8" "vermin==1.9.2" "setuptools==80.9.0" "uv==0.13.4"
 
       # The full screen also runs under the 3.8 floor: the end-to-end tests
       # start install.py with the interpreter that runs them.